Biomechanics final

The muscle fiber is surrounded by the _____, the fascicle is surrounded by the _____, and the muscle as a whole is surrounded by the _____.

Endomysium, Perimysium, Epimysium

Which muscle would not be strengthened by wrist flexion exercises?

Extensor indicis

Force-Velocity Relationship Isometric:

External load equals maximum force muscle can exert

Which muscle has its origin on the medial epicondyle of the humerus and causes ulnar deviation?

Flexor carpi ulnaris

Which phrase best describes "stress?"

Force per unit area

The center-edge angle is measured in the ___ plane, and the acetabular anteversion angle is measured in the ___ plane.

Frontal, Transverse

_____ attaches muscle to bone, and _____ attaches bone to bone.

Tendon, Ligament

Wolff of Wolff's law was

a German anatomist.

What type of joint is the knee?

a double condyloid joint

collagen has

a high tensile stiffness and strength

Epimysium surrounds

entire muscle

Ultimate strain is the same as ultimate elongation.

false

t/f A cane is best positioned on the ipsilateral side of the affected hip.

false

t/f A dislocated GH joint is also known as a separated shoulder.

false

t/f According to Rockwood, there is a large amount of relative motion that occurs between the clavicle and the acromion.

false

t/f Anthropometry, ground reaction forces, and muscle forces contribute as the primary inputs to inverse dynamics.

false

t/f Articular cartilage assists with transmitting tensile forces across the joint

false

t/f Cartilage consists of tough fibrous connective tissue that binds bone to bone

false

t/f Concentric muscle activity controls the lowering phase of the bench press.

false

t/f Excessive anteversion of the hip, such as 40 degrees, would result in a toeing-out appearance.

false

t/f Frontal plane knee motion is considered joint laxity.

false

t/f Hyaline cartilage is highly vascular.

false

t/f If a second stimulus occurs in a motor unit before the first twitch has subsided, the muscle will not respond to the second stimulus.

false

t/f In non-weight bearing, the talus is typically stationary and the mortise moves on the talus.

false

t/f Inversion and eversion occur about the oblique axis of the transverse tarsal joint.

false

t/f Most muscles contain only one type of muscle fiber.

false

t/f Posterior tibial muscles fire during early stance to prevent foot slap.

false

t/f Tendons can withstand multidirectional loading.

false

t/f The ACL resists posterior tibia translation.

false

t/f The collagen molecule consists of one alpha-1 chain and two identical alpha-2 chains.

false

t/f The distance between right and left heels describes stride length.

false

t/f The elbow joint reaction force is greater during flexion than extension.

false

t/f The force of the quadriceps is generally less than the force of the patella ligament.

false

t/f The gastrocnemius is the strongest plantar flexor of the foot and ankle.

false

t/f The hip joint is a 4 degree of freedom ball-and-socket-joint.

false

t/f The knee has 1 degree of freedom.

false

t/f The orientation of collagen fibers in ligaments are parallel while the orientation of collagen fibers in tendons are multidirectional.

false

t/f The ratio of scapulothoracic to glenohumeral motion is 2:1.

false

t/f The reaction forces on the ankle joint during gait are less than or equal to those at the hip and knee.

false

t/f The scapulothoracic joint is a true joint (i.e., has an axis of rotation).

false

t/f The stance phase consists of 75% of the gait cycle while the swing phase consists of 25% of the gait cycle (assume normal gait).

false

t/f The surface area of the medial tibial plateau is equal to the surface area of the lateral tibial plateau.

false

t/f The two types of osteoblasts are osteocytes and osteoclasts

false

t/f The type of collagen found in hyaline cartilage is the same as that found in bone.

false

t/f The wrist is made up of 12 carpal bones.

false

t/f The wrist is proximal to the elbow.

false

t/f There is only 1 double support phase during running, while walking has 2 double support phases in a gait cycle.

false

t/f When the body is in anatomical position, the palms face inward toward the trunk.

false

t/f deep zone of cartilage is the thickest zone

false

_____ wear occurs when there is an accumulation of microscopic damage within the bearing material under repetitive stressing.

fatigue

glenoid labrum

fibrocartilage ring that circles the cavity and deepens glenoid cavity

Extensors stronger than

flexors throughout the range of motion

motions of shoulder complex

forward flexion, extension, abduction, external and internal rotation, scapular plane elevation

Anterior

front, ventral

Performing a jumping jack occurs primarily in which anatomical plane?

frontal

Select the term that best describes the study of the body components needed to achieve or perform a human movement or function.

functional anatomy

water allows movement of

gas, nutrients, waste products

The ankle _________ power during push off.

generates

Internal joint moments account for the contributions of force generated by all of the following, except

gravity

High heels or narrow shoes can result in

hallux valgus

Ulnar flexion

hand toward the little finger

Radial flexion

hand toward the thumb

The talocrural joint

has primary motions of dorsiflexion/plantarflexion.

Osteocytes

have long extensions that reach out and connect to other osteocytes; have a mechanosensory and communicative function that allows them to sense strain and direct osteoclast activity

The neurovascular supply of tendons and ligaments are important for

healing, metabolism, proprioception

Symptoms of posterior tibial tendon dysfunction include all of the following except

heel varus

At _____ rates of loading, when bone tissue cannot deform fast enough, an injury can occur.

high

Tendons can withstand high

high unidirectional loads

Proteoglycan highest concentration

in middle zone

Proteoglycan lowest concentration

in superficial and deep zones

One may experience a femoral neck fracture due to all of the following except (high repetitive loading, overuse, muscle fatigue, increased bone mass)

increased bone mass

In the patellofemoral joint, the quadriceps muscle force ______ with knee flexion.

increases

Sufficient rest restores

initial signal content and amplitude

___ motion primarily occurs at the subtalar joint.

inversion/eversion, adduction/abduction

The right arm is ______ to the right leg.

ipsilateral

hysteresis

is a characteristic of ligaments and tendons.

The scapulothoracic joint

is an articulation between the scapula and thorax.

The path of the knee axis of rotation

is semicircular

The shoulder girdle

is the most dynamic and mobile joint. acts with the elbow to position the hand in space. attaches the upper extremity to the trunk.

Holding a box while waiting for your friend to open a door is an example of what type of contraction?

isometric

A cane is best used on the contralateral side of the affected hip because

it decreases the magnitude of the hip joint reaction force.

Which statement about articular cartilage is false?

it is composed primarily of elastin

The examination of the projectile characteristics of a high jumper is an example of which type of analysis?

kinematic

flow chart gait stuff

kinematics, anthropometry, ground reaction forces --> inverse dynamics --> joint forces, torques and powers--> modeling <--emg...modeling--> individual muscle forces

A _____ analysis would be used to determine the amount of force necessary to lift a 200-lb barbell in a squat.

kinetic

The major muscle groups of the elbow are

lateral extensor-supinators

Elastic materials exhibit a stress-strain relationship that is

linear

stress-strain O-P

linear region

stress-strain O

origin: resting biological material

The bone cells responsible for producing new bone are the

osteoblasts

Collagen fibers orientation

parallel

The primary mover for forward arm elevation in the scapular plane is the

supraspinatus

Which activity, when performed in moderate amounts, does the least to maintain bone strength? (weight lifting, running, swimming, soccer)

swimming

How does articular cartilage within a diarthrodial joint get its nourishment?

synovial fluid

Articular cartilage is found in

synovial joints

Tendons, ligaments, and bone that share collagen type I have similar

synthesis and degradation processes

All of the following are joints of the knee except

talocrural

Which of the following types of forces exerts a pull on the body acted upon?

tension

All of the following muscles comprise the rotator cuff except (Supraspinatus, Infraspinatus,Teres Major, Teres Minor, Subscapularis)

teres major

Biomechanical Properties of Tendons and Ligaments

•Viscoelastic •Sustain chiefly tensile loads during normal and excessive loading •If injured, damage is related to rate of loading and amount of load

Tendons and ligaments are stronger with higher rates of loading.

true

t/f A fall on an outstretched arm producing high loads in the elbow can cause an elbow fracture dislocation.

true

t/f A full gait cycle starts and ends with heel contact of the same foot.

true

t/f A haversian system is a long cylindrical structure in bone that serves as a weight-bearing pillar.

true

t/f A large Q-angle indicates knee valgus.

true

t/f A muscle can generate more force during contraction if it has been pre-stretched.

true

t/f Bone is a viscoelastic material

true

t/f Combined movement of the talocrural and subtalar joints allow for forward progression, balance, and walking on uneven terrains.

true

t/f Dart Thower's Motion (DTM) can be used to describe the wide movement arc in tasks with varying levels of fine motor control and force demands.

true

t/f During gait the upper body had sinusoidal displacements in 3 planes.

true

t/f During swing phase the hip joint reaction force is approximately equal to body weight.

true

t/f Hip joint range of motion decreases with age due to changes in motor control.

true

t/f If one reaches sideways to a shelf balancing on one foot the abductor force must increase to counterbalance as compared to standing on two feet.

true

t/f In a sarcomere, the dark bands are myosin, and the light bands are actin.

true

t/f In extremes of motion the capsular ligaments help prevent dislocation of the hip.

true

t/f Joint power is the product of the internal moment and joint angular velocity.

true

t/f Ligaments, such as the ACL, can have extensive macrofailure even when it's in continuity.

true

t/f Mechanotransduction occurs in both tendons and ligaments.

true

t/f Meniscus is an example of fibrocartilage

true

t/f Normal neck-to-shaft angle in the frontal plan is approximately 125 degrees.

true

t/f Scapular winging occurs when you have weakness or injury of the subscapularis or serratus anterior muscles.

true

t/f Structural defects such as a fibrillation are destructive results from the wear of cartilage

true

t/f Surface EMG detects the electrical activity resulting from the sum of the muscle action potentials from many motor units within the most superficial muscle.

true

t/f Tendons and ligaments display hysteresis during tensile testing that increases with a greater number of cycles, indicating energy loss, deformation, and molecular disruption.

true

t/f The 2 primary phases of a gait cycle are stance and swing.

true

t/f The anterior talofibular ligament is the most commonly sprained ankle ligament.

true

t/f The articulations of the transverse tarsal joint are between the talus and navicular and the calcaneus and cuboid bones.

true

t/f The foot has 3 functional units: the hindfoot, midfoot, and forefoot.

true

t/f The glenohumeral joint is inherently unstable.

true

t/f The glenoid labrum is composed of a fibrocartilaginous rim that deepens the glenoid by 50%.

true

t/f The primary elbow flexor is the brachialis, whereas the primary extensor is the triceps.

true

t/f The primary motion of the knee is in the sagittal plane.

true

t/f The proximal humerus head and glenoid fossa is covered with hyaline cartilage.

true

t/f The quadriceps muscle group is the major muscle force contributor to knee flexion-extension.

true

t/f The resultant joint force on the tibia is greater during stair descent than stair ascent.

true

t/f The sternoclavicular joint is a synovial joint.

true

t/f The tarsometatarsal joints are also known as the Lisfranc joints.

true

t/f The tibialis posterior is the strongest inverter of the foot and ankle.

true

t/f Viscoelastic materials possess both fluid- and solid-like properties.

true

t/f Walking base is analogous to step width.

true

t/f Water is the most abundant component of cartilage

true

t/f Women have higher hip joint stress than men.

true

Pronation

turn palms backward

Supination

turn palms frontward

Flexor group nearly

twice as strong as extensor

Which muscle fiber type is only oxidative?

type I

Grip strength can be enhanced by positioning the wrist in _____ and slight hyperextension.

ulnar flexion

stress-strain U

ultimate stress: max stress with strain applied

Which is not part of the axial skeleton?

upper extremities

The joints of the shoulder include

acromioclavicular glenohumeral sternoclavicular scapulothoracic

Signs of osteoarthritis include all of the above except (cartilage growth, decreased joint space, osteophyte formations, changes in bone surfaces)

cartilage growth

waters movements influences

cartilage mechanical behavior.

total compressive knee forces range between

2-4 %BW

During normal gait, the knee displays maximum flexion at

70% of the gait cycle

Wolff's Law •Deposition

-Response to increased stress -Osteoblasts dominate •Weight-bearing exercise

Myofibrils

-Rod-like strands of contractile filaments -Many sarcomeres in series

•Gait involves motion in 3 planes.

-Rotation occurs during swing and stance phases.

•3 degrees of freedom

-Triaxial -Example: Shoulder

cortical bone is what % of skeleton

80%

The slope of the linear portion of a stress-strain curve represents which term?

elastic modulus

Skeletal muscle is

most abundant tissue in human body

Ipsilateral

on the same side

H zone:

only thick filaments and titin in t

stress-strain P

proportionality limit: point when material stops acting linearly

•To understand cartilage response to stress:

-Intrinsic mechanical properties must be determined. -Compression, tension, and shear are considered.

•Olecranon bursitis

-Irritation of the olecranon bursae -Commonly caused by falling on the elbow

•PG interacts with collagen:

-It forms a porous matrix. -This matrix is swollen with water.

•Knee joint:

-Largest and most complex -Composed of tibiofemoral and patellofemoral joints

•Sagittal

-Left and right halves -Mediolateral axis

•Mechanical behavior is influenced by bone geometry:

-Length -Cross-sectional area -Distribution of bone tissue -Area moment of inertia

motion of sternoclavicular joint

protraction-retraction, elevation-depression, rotation

•Force produced in muscle influenced by:

-Length-tension -Load-time -Force-time relationships

•Eversion

-Lift lateral edge of the foot

•Inversion

-Lift medial edge of the foot

•Shoulder stability maintained by:

-Ligaments -Integrity of shoulder capsule -Negative intra-articular force

•Interstitial fluid pressurization influences:

-Load-bearing capacity -Lubrication capacity

•Bennett fracture

-Longitudinal fracture of the base of first metacarpal

The SC joint articular disc and ligaments

provides stability, allows rotation of the clavicle

Tenocytes are

responsible for remodeling tendons.

Linear motion is also known as _____ motion.

translational

The longitudinal axis is orthogonal to which plane?

transverse

tension fracture pattern

transverse crack

stress strain: Bone initially exhibits an

elastic response. -Deformation in response to loading -Load removed à return to original shape/length

•Rotation of the scapula produced by synergistic contractions

-Lower Serratus -Anterior Lower Trapezius -Upper Trapezius -Levator Scapulae Upper Serratus Anterior

•Summary: Human movement analyzed using:

-Qualitative analysis -Quantitative analysis

•Aging induces:

-Reduction in amount of cancellous bone -Decrease in thickness of cortical bone -Diminution of bone toughness -Reduction in strength -Decrease in stiffness

•Wolff's Law

-Remodeling of bone is influenced and modulated by mechanical stresses

Wolff's Law •Resorption

-Response to decreased stress -Osteoclasts dominate •Disuse, immobilization, microgravity

Nociception

-Response to harmful stimuli

•Radioulnar joints

-Articulations between the ulna and radius •Proximal and distal -Pronation, supination -Interosseous membrane •Thin layer of tissue running between the ulna and radius -Medial and lateral epicondyles

•Swing phase

-Initial swing -Mid swing -Terminal swing

joints of wrist: Interphalangeal

-Articulations between phalanges

•Bone is made of:

-Inorganic portion of mineral salts (60% weight) *Makes bone hard and rigid -Organic matrix of collagen (30% weight) *Makes bone flexible and tough *Water (10% weight)

principles determining best exercise for bone

(1) The forces and the rate of force development should be high (impact activities) 2) the number of impacts does not need to be great because bone becomes desensitized to mechanical stimulus rather quickly 3) the sensitivity to mechanical stimulus recovers with rest 4) loading from different directions increases osteogenesis.

Orthopaedic Measurements Torsion angle

(between axis through the femoral head and neck and the axis through the femoral condyles)

Which of the following is a type femoroacetabular impingement?

*Cam *Pincer *Combined

Tennis elbow (lateral epicondylitis) is

*Due to repetitive microtraumas. *More common than medial epicondylitis. *Often involves injury to the extensor carpi radialis brevis muscle.

Bone functions to

*Provide rigid kinematic links *Protect internal organs *Provide muscle attachment points *Facilitate muscle movement

What is the function of the rotator cuff?

*Provide stability for the glenohumeral joint. *Depress the humeral head. *Serve as a functional synergist to more superficial shoulder muscles.

The following clinical angles are used to measure the hip joint:

*Torsion angle *Angle of inclination *Center-edge angle *Acetabular anteversion angle

The biomechanical behavior of a viscoelastic material

*Varies with the rate at which the load is removed *Varies with strain rate (activity intensity) *Varies with the rate at which the load is applied

The medial longitudinal arch of the foot

*acts like a beam and a truss. *is elevated through the windlass mechanism of plantar fascia. *is supported by the posterior tibial tendon.

Hip joint reaction forces can be decreased by

*altering the center of motion in a hip implant *changing the lever arm of the abductor through surgery

The hallux

*bears the most pressure at toe-off during gait *has up to 85 degrees of dorsiflexion *is the primary site for bunions and turf toe *is the technical name for the great toe

Which of the following is a primary vector in the simplified free-body diagram of the hip?

*body weight *hip reaction force *abductor muscle force

Wear of articular cartilage can be

*fatigue wear *interfacial wear *joint impact loading

Motion analysis methods

*integrate kinematics, kinetics and EMG *involve 3D measurements *can be used to measure normal or pathologic gait.

The acromioclavicular joint

*is a synovial joint. *is subjected to high loads transmitted from the chest musculature to the upper extremity. *is located between the lateral end of the clavicle and the acromion.

The deltoid ligament ___.

*is located on the medial side of the ankle *is stronger than the lateral ankle ligaments *maintains the integrity of the syndesmosis *prevents ankle eversion and abduction

Stability for the glenohumeral joint comes from the following:

*joint capsule *rotator cuff muscles *ligaments

Pathological gait patterns are primarily caused by

*musculoskeletal system impairments *central nervous system disorders *pain

Carpal tunnel syndrome

*often occurs due to repeated wrist flexion *involves median nerve compression

The foot and ankle

*provides an interface between body and ground. *absorbs and translates force with stability. *is used to propel the body.

Tissue engineering strategies incorporate ____ to grow fabricated tissues.

*scaffold material *appropriate cell source *culture environment with chemical and biophyscial stimuli

Shoulder stability is preserved by

*shoulder capsule integrity. *negative intra-articular pressure. *ligaments and muscles.

Stability of the knee is provided by

*the menisci *the ligaments *the muscles

Sliding of the tibiofemoral joint occurs

*throughout the range of motion *on the medial side *on the lateral side

The joints of the elbow include

*ulnohumeral joint *radiohumeral joint *2 radioulnar joints

Load relaxation experimental tests are used to determine the

*viscoelastic behavior of tendons. *time-dependency of ligaments. *nonlinear behavior of tendons and ligaments.

•3rd Degree sprain ligament injuries

- severe pain; unstable joint; total rupture or most collagen fibers ruptured; functionless

•Medial tension syndrome

-"Pitcher's elbow" -Medial elbow pain from excessive valgus forces •May include ligament sprain, medial epicondylitis, tendinitis, avulsion fracture

•Cartilage is a highly stressed material

-20 MPa contact stress in hip when rising from a chair -10 Mpa during stair climbing

Orthopaedic Measurements •Acetabular anteversion angle

-20° coverage of the femoral head in the horizontal plane

Orthopaedic Measurements •Center-edge angle (angle of Wiberg)

-35°-40° coverage of the femoral head in frontal plane

•Linear motion

-AKA translation or translational motion -Movement on straight or curved pathway -All points move same distance, same time

•Hyperabduction

-Abduction past 180° point

Excitability

-Ability to respond to stimulation

Elasticity

-Ability to return to resting length after being stretched -Protective mechanism

Contractility

-Ability to shorten when it receives sufficient stimulation -Unique to muscle tissue

•Extensibility

-Ability to stretch/lengthen beyond resting length -Protective mechanism

•Fatigue wear:

-Accumulation of microscopic damage within the bearing material under repetitive stressing

•Hip joint composed of:

-Acetabulum -Femoral head -Femoral neck -Acetabular labrum -Hip capsule -Muscles surrounding the hip

•Length-tension relationships influenced by:

-Active contractile components -Passive (series and parallel elastic) components

•Hyperadduction

-Adduction past 0° point

•Limited vascularization

-Affects their metabolic activity -Critical for healing in repair

•Articular cartilage

-Also called "hyaline" -Covers joint ends at articulations -60% to 80% water Contains collagen and proteoglycan

•Joint reaction forces can be reduced by:

-Altering the center of motion in the prosthetic design -Slightly changing abductor muscles lever arm through surgery

•Carrying angle

-Angle between the ulna and the humerus with the elbow extended -10° to 20°

•Biomechanics:

-Application of mechanics to biologic systems -More specific than kinesiology

summary Bones

-Are composed of compact and spongy tissue -Respond according to Wolff's law -Are both anisotropic and viscoelastic -Most bone fractures are produced by a combination of several loading modes -Muscle contraction affects stress patterns in bone -Are affected by aging with diminished bone toughness, strength and stiffness

•Differences in forces in gait:

-Are found in extension and adduction -Moments are higher in women. *This suggests a narrower step width relative to pelvic width in women.

joints of the wrist: intercarpal

-Articulation between a pair of carpals

radiohumeral joint

-Articulation between the radius and humerus -Capitulum •Eminence on the distal end of lateral epicondyle Articulates with the head of radius at the elbow

joints of the wrist: midcarpal

-Articulation between two rows of carpals

joints of wrist: carpometacarpal

-Articulations between carpals and metacarpals

joints of wrist: Metacarpophalangeal

-Articulations between metacarpals and phalanges

•Bone is viscoelastic:

-At high loading rates: -Bone is stiffer -Bone sustains higher loads -Bone stores more energy

•Tendons functions:

-Attach muscle to bone -Transmit tensile load from muscle to bone -Produce joint motion -Promote joint stability -Contribute in maintaining body posture

•Shoulder girdle:

-Attaches upper extremity to trunk -Acts with elbow to position hand in space -Is the most dynamic and mobile joint

•Ligaments and joints capsules functions:

-Augment mechanical stability of joints -Guide joint motion -Prevent excessive motion -Contribute to proprioception

•Mallet finger

-Avulsion of finger extensor tendons at the distal phalanx •Result of forced flexion

•Jersey finger

-Avulsion of finger flexor •Result of forced hyperextension

•Absolute

-Axes intersect in the center of a joint

•Interfacial wear:

-Bearing surfaces come into direct contact, with no lubricant film separating them.

•2 degrees of freedom

-Biaxial Example: Wrist

Other muscles act on the shoulder joint

-Biceps brachii -Back muscles: trapezius, latissimus dorsi, levator scapulae, rhomboids, serratus anterior, intercostals

Tendons vascular supply

-Blood vessels represent 1-2% of ECM -White color -Factors that contribute to blood supply •Anatomic location, morphology, prior injury, level of physical activity

•Functional anatomy

-Body components necessary to achieve goal -Focus on function -Example: Analysis of biceps curl

•Ectopic bone deposits in muscle (myositis ossificans)

-Bone formation away from normal site

•Running follows a sequence similar to normal gait except

-Both feet come off the ground immediately after terminal stance on one side and before initial contact on the other.

Fatigue can induce bone fracture:

-By repeated load application -When loading precludes remodeling -This is called fatigue fracture

•Tendon made of dense connective tissue:

-Cellular material (20%) -Extracellular matrix (80%) of: Water (mainly), collagen, elastin, PG, proteins

•When motor unit fatigues

-Change in frequency content -Change in amplitude of EMG signal

hip range of motion decreases with age due to:

-Changes in motor control -Loss of motor units -Decreases in fast twitch muscle fibers

•4 zones structure of bony insertion

-Collagen fibers -Fibrocartilage -Mineralized fibrocartilage -Cortical Bone

•Same general composition as tendons with few differences:

-Collagen fibers are more multidirectional: -Ligaments mainly support stress in one direction. -Ligaments also support small stresses in other directions.

•Horizontal abduction

-Combination of extension and abduction

•Horizontal adduction

-Combination of flexion and adduction

•When ultimate tensile strength surpassed:

-Complete failure occurs rapidly -Load-bearing ability decreases substantially

•Gait is a functional task requiring:

-Complex interactions and -Coordination among major joints of

•Types of muscle contractions:

-Concentric, eccentric, isometric

Sarcoplasma

-Cytoplasm of muscle cell

•Dorsiflexion

-Decrease angle between the foot and the shank

Flexion

-Decreasing joint angle

•Open section defects

-Defect whose length exceeds the diameter of the bone

•Stress raisers

-Defect whose length is less than the diameter of the bone (screws)

Tendinosis

-Degenerative condition that is asymptomatic -Inflammation -Can lead to tendon rupture

•Effectiveness of strengthening/stretching exercises

-Depends on the position of arm •Strongest in semiprone

•Biomechanical Functions fascia

-Dissipation of loads to reduce wear and tear, -Facilitate linkage to form mechanical chains -Improve muscular effciency via force transmission to noncontractile tissues (tendons)

•Pronation of the foot

-Dorsiflexion at the ankle -Eversion in the tarsals -Abduction of the forefoot

Coactivation of agonist-antagonist muscles occurs:

-During periods of kinematic transition -When a joint may be reversing direction of rotation

•Ulnar-humeral joint

-Elbow -Articulation between the ulna and the humerus

Cartilage treated as a biphasic material with:

-Interstitial fluid phase -Porous-permeable solid phase

Upper extremity (shoulder, elbow, wrist and hand) is obviously important in

-Everyday activities •Pushing up out of a chair •Carrying, lifting -Sporting/leisure activities •Swimming, throwing, striking (golf, volleyball)

•Kinetics

-Examines forces

•Kinematics

-Examines motion with respect to space and time -Position, velocity, acceleration

•Statics

-Examines systems not moving or moving at a constant speed -Equilibrium: No acceleration -Example: Spaceship gliding through space

•Dynamics

-Examines systems that are being accelerated -Example: Softball pitch

anisotropically

-Exhibits different mechanical properties -Because structure is different in transverse and longitudinal directions

•Hyperextension

-Extension beyond normal range

T-tubules

-Extension of sarcolemma that protrudes into muscle cell -Also called transverse tubule

Gait Deviations: Trendelenburg gait

-Failure of the hip abductors to produce sufficient abductor moment during loading response and terminal stance -Lateral drop of the pelvis on contralateral side

•Precision grip

-Fine-movement hand position -Minimally flexing fingers around an object

Muscle Architecture parallel

-Flat, fusiform, strap, radiate (convergent) circular

Plane

-Flat, two-dimensional surface

•Hyperflexion

-Flexion beyond normal range

•When load is applied to cartilage:

-Fluid runs outside the matrix. -It protects against excessive stress and strain.

•Injury mechanisms influenced by:

-Force produced by muscle contraction -Cross-sectional area of tendon / muscle

•Glenohumeral is a major load-bearing joint: when holding arm in outstretched position

-Forces equivalent to ½ body weight

•Fibrocartilage

-Found where articular cartilage meets a tendon or ligament -Meniscus, articular disc: Fibrocartilage structure •Intervertebral discs, jaw, knee

•Frontal (coronal)

-Front and back halves -Anteroposterior axis

•Elevation of the arm involves motion at:

-Glenohumeral joint -Scapulothoracic joint The ratio of GH to ST motion is 2:1

Shoulder girdle consists of:

-Glenohumeral, acromioclavicular, sternoclavicular, scapulothoracic joints -Muscles acting on these joints

•Glenohumeral is a major load-bearing joint: forces necessary for arm elevation

-Greatest at 90° of elevation -Equivalent to 8.2 times arm weight

•Concentric

-Gripping is concentric for finger flexors -Sit ups are concentric for abdominal muscles in the up motion (flexion) -Rowing is concentric in the big push phase for shoulder extensors, scapular adductors and elbow flexors

Muscular Actions, flexion of the knee

-Hamstrings •Biceps femoris •Semimembranosus •Semitendinosus

•Muscular actions

-Hand flexion/extension -Hand radial/ulnar flexion -Finger flexion/extension -Finger abduction/adduction -Thumb flexion/extension -Thumb abduction/adduction -Thumb opposition

glenohumeral inferior ligament

-Has most important functional significance because -Acts as primary stabilizer when arm abducted at 90°

•Axial skeleton

-Head -Neck -Trunk

•Lateral flexion

-Head or trunk only -Example: Head tilts sideways

•Range of motions necessary in daily activities:

-Hip flexion of at least 120º -Abduction of at least 20º -Internal and external rotations of at least 20º

•cortical bone: Lamellae

-Hollow tubes placed inside one another -Composed of collagen fibers running in a single direction

•Axes

-Imaginary lines that intersect at right angles

•Why condition hand region?

-Improve grip strength -Enhance wrist action for throwing, striking -Prevent injury

•Relative angle

-Included angle between two segments

•Tissue engineering is:

-Incorporating an appropriate cell. -This cell will grow fabricated tissues. -These tissues will be used for repair and replacement of damaged or diseased tissues and organs.

•Plantarflexion

-Increase angle between the foot and the shank

•Articular cartilage functions:

-Increase load distribution area -Allow movement while reducing friction and wear

cartilage functions

-Increases joint stability -Distributes load in the joint Reduces contact stress by 50%

•Extension

-Increasing joint angle

Segmental Kinetics: internal joint moments

-Indicate net moment of force generated by muscles, bones, soft tissues -Counteract tendency for joint rotation due to gravity

•Tenosynovitis

-Inflammation of sheath surrounding the tendon

•Osteochondritis dissecans

-Inflammation of the bone and cartilage resulting in splitting pieces of cartilage into the joint

•Ratio of abductor muscle force lever arm (c) ⁄ gravitational force lever arm (b):

-Influences the magnitude of the joint reaction force on the femoral head -Is of importance in respect to prosthetics

•Stance phase includes

-Initial contact -Loading response -Mid stance -Terminal stance, pre-swing, toe off

•Cartilage failure progression relates to:

-Magnitude of imposed stresses -Total number sustained stress peaks -Changes in intrinsic molecular and microscopic structure of collagen-PG matrix -Changes in intrinsic mechanical property of tissue *associated with decreased cartilage stiffness and increased cartilage permeability.

•Load-bearing structures:

-Mainly tibial plateaus -Cartilage, menisci, ligaments also carry force -Menisci aid distributing stresses, reducing pressures on tibial plateau

•Articular cartilage is multiphasic:

-Matrix of collagen and proteoglycan (25%) -Free interstitial fluid (75%) -Ion phase

•Tetanic contraction:

-Maximal tension sustained due to summation

•Rotation

-Medial (internal) or lateral (external) -Right/left for the head and trunk

•Tendons and ligaments have intricate neurovascular supply important in:

-Metabolism -Healing -Proprioception Pain generation

stress strain: Continued loading past yield point- plastic response

-Microtears and debonding -Load removed à permanently deformed

Aging muscle remodeling

-Modifies muscle architecture -Reduces muscle mass and force production

•24 muscles cross elbow

-Most of these muscles capable of multiple movements at multiple joints -Muscles better at some movements than others

•Angular motion

-Motion around some point

•Hypothenar eminence

-Mound on ulnar side of the palm created by intrinsic muscles acting on the little finger

•Circumduction

-Movement in a conic fashion

•Abduction

-Moving away from midline

•Adduction

-Moving toward midline

Force-Velocity Relationship Concentric:

-Muscle contracts with maximal speed when load is negligible

•Eccentric

-Muscle visibly lengthens while producing tension •Lowering phase of squat

Concentric

-Muscle visibly shortens while producing tension •Up phase of a sit-up

•Deformations are used to characterize materials:

-Normal and shear stresses -Normal and shear strains -Elastic and plastic deformations

•Degree of freedom

-Number of planes in which a joint has the ability to move

•Gait cycle or stride:

-Occurrence of an event on one lower limb until next occurrence of same event on same lower limb -Demarcated by sequential ipsilateral initial contact -Stance phase represents 60% of stride Swing phase represents 40% of stride

•Major events during stance phase

-Opposite Heel rise -Opposite toe off Opposite initial contact

•Shoulder musculature made of layers:

-Outermost layer: deltoid, pectoralis -Rotator cuff layer: supraspinatus, infraspinatus, subscapularis, teres minor

•Tendinitis

-Painful tendon dysfunction

Fiber Organization fusiform

-Parallel fibers and fascicles -High speed of contract, force production -ACS = PCS •Anatomical cross-section (ACS) •Physiologic cross-section (PCS) -Sartorius, biceps brachii, brachialis

•Dynamic stability occurs via:

-Passive tension from muscles -Barrier effect of contracted muscles -Redirection of joint force toward center of glenoid

Sample joint force

-Patellofemoral compressive force: 0.5 to 1.5× BW in walking, 3 to 4× BW in climbing, 7 to 8× BW in squats -Tibiofemoral compressive forces often >1,000 N -Tibiofemoral shear forces often >600 N

•Motion limitations or disorders of motor control affecting one lower limb segment may alter:

-Patterns of movement and -Motor control at all other joints during gait

•Proprioception

-Perception of movement and spatial orientation of the body

muscle fatigue results from

-Peripheral (muscular) mechanisms -Central (nervous) mechanisms

•Cardinal planes

-Planes positioned at right angles and intersecting the center of mass

•Supination of the foot

-Plantarflexion at the ankle -Inversion in the tarsals -Adduction of the forefoot

Biomechanical Properties of ligaments

-Pliant and flexible -Strong and inextensible

•Axis of rotation

-Point about which movement occurs -Perpendicular to plane of motion

•Origin

-Point of intersection of axes

•Power grip

-Powerful hand position -Maximally flexing fingers around an object

•Biomechanical properties also influenced by:

-Pregnancy -Immobilization -Systemic conditions and pharmacologic agents

•Carpal tunnel syndrome

-Pressure and constriction of the median nerve •Caused by repetitive actions at the wrist

Segmental Kinetics: joint power

-Product of joint angular velocity and internal moment -Indicates generation or absorption of mechanical energy by muscle groups and other soft tissues

•Skeletal muscle functions:

-Provide strength -Distribute loads -Protect skeleton by absorbing shocks -Maintain body posture

Muscular Actions, Extension of the knee

-Quadriceps femoris •Rectus femoris •Vastus intermedius •Vastus lateralis •Vastus medialis

•Knee muscles exert considerable force

-Quadriceps tension: 1 to 3× BW in walking, 4× BW in stair climbing, 5× BW in squat

•Biomechanics requires an understanding of concepts such as:

-Scalars, vectors, tensors -Force, torque, moment -Newton's laws -Free-body diagrams -Equilibrium (∑F = 0 and ∑M = 0)

•Kinesiology:

-Scientific study of human movement -Anatomical, physiologic, psychological, biomechanical

•Relative

-Segment movement described relative to the adjacent segment

Effect of External Support on Hip Joint Force Reaction Force: cane

-Should be used on the opposite side -Frequently decreases magnitude of hip JRF

•Fundamental position

-Similar to anatomical position -Arms more relaxed -Palms face inward

During gait Upper body:

-Sinusoidal displacements in 3 planes -Trunk and pelvis rotate in opposite directions -Head remains stable -Swinging of arms: *Shoulder flexion-extension and rotation *Elbow flexion-extension *Forearm prono-supination

•Bone can remodel

-Size -Shape -Structure

•When subject to constant low load over long time:

-Slow deformation, or creep

trabeculae cancellous bone

-Small, flat pieces of bone that serve as small beams between the spaces -Adapt to the direction of the stress on the bone

•Trigger finger

-Snapping during flexion and extension of fingers •Created by nodules on tendons

•Movements limited by several factors

-Soft tissue, ligaments, joint capsule, muscles

•Sarcoplasmic reticulum

-Specialized endoplasmic reticulum of muscle cells

•Tenocytes

-Specialized fibroblasts -Have multiple extensions that stretch within the ECM -Primary role is to control tendon metabolism and to respond to the mechanical stimuli applied to the tendon •Particularly tensile loads that serve as signals for collagen production - a process known as mechanotransduction

•Gait cycle consists of 2 phases:

-Stance phase -Swing phase

•Anatomical position

-Standard reference point -Palms face front

•Boutonniere deformity

-Stiff proximal interphalangeal articulation •Caused by injury to the finger extensor mechanism

•Aging results in decline in mechanical properties:

-Strength -Stiffness Ability to withstand deformation

•Tendons and ligaments have viscoelastic behavior:

-Strength and stiffness increase when loading rate increases.

•When subject to constant elongation:

-Stress relaxation

•Anatomy

-Structure of the body -Focus on structure -Example: Study of biceps brachii

Collagen Presents 3 zones:

-Superficial tangential zone (10% to 20% thickness) -Middle zone (40% to 60% thickness) -Deep zone (30% thickness)

•Glenohumeral ligaments:

-Superior, middle, inferior -Are extensions of joint capsule -Are critical to shoulder stability and function

•Hip joint:

-Supports weight of upper body -Has ability to transmit forces vital to normal functioning of human body -Is a ball-and-socket joint -Provides stability and mobility -Is commonly injured

Tibiofemoral joint kinematics

-Surface motion in 3 planes -Largest motion in sagittal plane •-3° to 155° flexion -Transverse plane is rotational laxity -Knee joint flexion affects ROM in transverse and frontal planes

Biomechanical Properties of Tendons

-Sustain high tensile forces resulting from muscle contraction during joint motion -Flexible to angulate around bony surfaces

•Sternoclavicular joint:

-Synovial joint -Connects medial end of clavicle to manubrium -Links upper extremity to thorax -Articular disc and ligaments: *Provide stability *Allow significant rotation of clavicle

•Acromioclavicular joint:

-Synovial joint -Little motion between clavicle and acromion

during gait Ankle and foot joints motion:

-Talocrural joint: only plantar/dorsal flexion *Because bony morphology -Subtalar, midtarsal, phalangeal motion provide: *Adaptation to support surface *Rigidity for propulsion

•Isometric

-Tension produced without visible change in joint angle •Holding arms out to sides

Sarcolemma

-Thin plasma membrane branching into muscle

•Overuse injuries more common than trauma

-Throwing, tennis serve

•The knee joint region consists of three articulations (joints)

-Tibiofemoral -Patellofemoral -Tibiofibular

•Bone functions:

-To protect internal organs -To provide rigid kinematic links -To provide attachment points for muscles -To facilitate muscle action and movement

forearm injury: Rupture

-Torn or disrupted tissue •Biceps brachii during fall with arm extension, forearm extension and forearm pronation

•Knee functions:

-Transmit loads -Facilitate positions and movement of the body -Provide movements for activities involving the leg

Gait Deviations: Lateral lurch

-Trunk displaced toward the affected stance limb during loading response -Excessive lateral displacement to reduce the required hip abductor moment by decreasing the abductor moment arm

joints of the wrist: distal radioulnar

-Ulna makes NO contact with carpals -Does NOT participate in wrist movements

•1 degree of freedom

-Uniaxial -Example: Elbow

Muscle Architecture pennate

-Unipennate, bipennate, multipennate

•Glenohumeral joint:

-Unstable because glenoid fossa is shallow -Stable from capsular, muscular, ligamentous structures

•Transverse (horizontal)

-Upper and lower halves -Longitudinal axis

•Appendicular skeleton

-Upper extremities Lower extremities

•Summary: Movement described:

-Using anatomical movement descriptors -In relation to planes of motion

Endomysium

-Very fine sheath covering individual fibers

•Which activities provide substantial mechanical stress to bones?

-Weight lifting -Running -Swimming -Football

joints of the wrist: radiocarpal

-Wrist -Ellipsoid joint •Flexion/extension, radial/ulnar flexion

wrist exercises

-Wrist curls -Gripping exercises -Stretching

positive coxa valga

1. decreased bending moment arm decreases bending moment; decreases shear force across femoral neck 2. increased functional length of hip abductor muscle

Type IIB muscle fibers

-fast-twitch glycolytic •White •Sprinters, jumpers

Type IIA muscle fibers

-fast-twitch oxidative-glycolytic •Intermediate

Force-Velocity Relationship Eccentric:

-force increases as the velocity of the lengthening increases

Osteoclasts

-large multinucleated cells that work to dissolve the bone in areas of microfracture

•During gait Knee joint motion

-mainly flexion-extension •Varus-valgus and rotations present to lesser extent

negative coxa valga

1. decreased moment arm for hip abductor force 2. alignment may favor joint dislocation

•1st Degree sprain ligament injuries

-negligible symptoms; some pain but no joint instability; no macroscopically observable disruption of the fibers

-Type I muscle fibers

-slow twitch oxidative •Red (because of high myoglobin content) •Endurance athletes

biomechanical properties of bone

-strong, stiff, and tough -Bone has a grain like wood -Bone behaves anisotropically

•Motion of thoracic and lumbar spine contributes

-to positioning the upper extremity in space -Enhances overall motion and function of the shoulder

hip jfr

-≥ 6 times BW during stance phase of gait cycle -= BW during swing phase of gait cycle -Increases with gait velocity -= 8 times BW during running or skiing

When holding the arm outstretched with shoulder abduction, the forces on the glenohumeral joint are equivalent to

0.5 times body weight

the most important mechanical properties bone

1. Strength 2. Stiffness 3. Toughness

•Each sarcomere is composed of:

1. The thin filaments (approximately 5 nm in diameter) composed of the protein actin 2. The thick filaments (about 15 nm in diameter) composed of the protein myosin 3. The elastic filaments composed of the protein titin 4. The inelastic filaments composed of the proteins nebulin and titin

negative of coxa vara

1. increased bending moment arm increases bending moment; increases shear force across femoral neck 2. decreased functional length of hip abductor muscles

positive of coxa vara

1. increased moment arm for hip abductor force 2. alignment may improve joint stability

Average walking velocity is

1.2 m/sec

Causes of Pathologic Gait Patterns

1.Pain 2.Central nervous system disorders 3.Musculoskeletal system impairments

Joint Dynamics Computations

1.The anatomic structures are identifed: defnitions of structures, anatomic landmarks, point of contact of articular surface, and lever arms involved in the production of forces for the biomechanical analyses. 2.The angular acceleration of the moving body part is determined. 3.The mass moment of inertia of the moving body part is determined. 4.The torque (moment) acting about the joint is calculated. 5.The magnitude of the main muscle force accelerating the body part is calculated. 6.The magnitude of the joint reaction force at a particular instant in time is calculated by static analysis.

angle of inclination coxa vara

105 degrees, more of a right angle

The minimal amount of tibiofemoral range of motion needed for performing activities of daily living is

117

Orthopaedic Measurements •Angle of inclination (neck-to-shaft angle)

125 degrees

angle of inclination coxa valga

140 degrees, more upright

how many degrees of freedom does the knee have

2 DOF

•Humans recycle how much of their bone mass every week

5%-7%

The hip joint reaction force is ____times body weight during stance phase of the gait cycle.

6

porosity cancellous bone

> 70%

Primary wrist motions are

2D

How many degrees of freedom does the hip have?

3

The shoulder moves in

3D

Give an example of a physiological tissue that corresponds with each of the components of muscle model

A and D: These components correlate to the series elastic components and they are modeling something like the tendon. Tendons connect muscle to bone, and the force is distributed along this direction. Tendons also have some elastic components as indicated by the name series elastic. B: This is the contractile component of the muscle model. The contractile component corresponds to the sarcomere of the muscle and specifically the actin and myosin that slide past each other and make the muscle contract. C: This the parallel contractile component of the muscle model. This can correspond to the tissues around the muscle like the endomysium. These tissues are also elastic.

muscle tension vs muscle length graph, components of graph

A(top dotted): total muscle tension, B(increasing line): passive muscle tension, C(bell curve): active muscle tension, D(top of bell to x axis height): resting length of the muscle. These curves relate to each other because the active and passive muscle tensions will add up to the total muscle tension.

In the sliding filament theory, what slides past one another during contraction?

Actin and myosin

load velocity curve for muscle what type of contraction

At point A, an eccentric contraction is being shown. This is known because the graph shows that to the left is maximum lengthening velocity which correlates with the lengthening during eccentric contraction. With high loads the velocity will increase for these contractions. Point C represents isometric contractions. This is when the external load will equal the maximum force that a muscle can generate. Point B demonstrates the concentric contraction. This is when the maximum shortening occurs, which again makes sense because in concentric contractions the muscle is being shortened. For the concentric contraction, the muscle will have the fastest contractions when the load is very small.

Tendons

Attach muscle to bone

Which muscle causes forearm supination?

Biceps brachii

21(c): Discuss the behavior of bone in tension and compression. Which one is better tolerated by bone? Why?

Bone is strongest under compression. This would make sense because while standing, there is a compressive load on a lot of our bones so it is important that our bones can support this compressive load. The reason that it is strongest in compression has to do with the structure of bone. Bone is composed of an osteon or haversian structure, meaning there are tubule structures formed around collagen fibers that provide a sort of pillar support for the bone. These support pillars are strongest under compression than tension. In order for bones to fail in tension the osteons would basically debond whereas in compression the osteons would have to crack.

Briefly explain the process of bone healing and remodeling following injury.

Bone remodels according to stress and use of the tissue. If the tissue is used a lot, bone will grow because osteoblasts will deposit bone. If the bone is not used a lot, them osteoclasts will remove the bone. After injury, it is likely that initially, the bone will resorb by osteoclasts, because they will be drawn toward the microfracture. Then, once the bone is resorbed, the osteoblasts will begin to deposit bone into the injured area. Then, eventually when the bone can be used and stress can be applied the bone will continue to grow by deposition.

Which of the following muscles does not cause wrist flexion?

Brachioradialis

Which ion is most responsible for facilitating muscle contraction?

Ca2+

Describe the biomechanical principles that explain why casting is a successful method to treat clubfoot deformity.

Casting is a successful method to treat clubfoot deformity because when applying the knowledge of creep and stress relaxation to the soft tissues in the deformed foot, it can be understood why this method would work. As the foot is put in a cast, there will be initial deformation. When this deformation is kept constant, the stress on the foot will decrease. This decrease in stress can allow continued treatment, until the foot returns back to its normal position.

A(n) _____ contraction occurs when tension develops in a muscle as it shortens, a(n) _____ contraction occurs when tension develops in a muscle as it lengthens, and a(n) _____ contraction occurs when tension develops in a muscle but it does not change length.

Concentric, Eccentric, Isometric

Ligaments

Connect bone to bone

In the three-component model of muscle, which component most closely corresponds to the sarcomere?

Contractile component

22(a): Describe how creep and load relaxation tests are conducted experimentally to measure a soft tissue, such as a tendon or ligament. What does each test tell you about the material properties of the tissue?

Creep test is conducted be applying a constant load to a soft tissue and measuring the changes in deformation over time. In many cases, there will be an initial increase in deformation, and then it will slow down a lot. For load relaxation, a constant strain or deformation would be applied to the tissue, and then stress would decrease and then slow down to a constant stress. These tests show the viscoelasticity of the tissue and show is they have both viscous and elastic characteristics over time.

Select the statement that best describes the force-velocity relationship of muscle performance:

In concentric muscle action, as velocity of contraction increases, the ability of muscle to generate force decreases.

Loading Rate and Fracture: clinical significance

Influences both fracture pattern and amount of soft tissue damage at fracture

Cancellous (or trabecular) bone

Inner part with loose mesh structure

Wear of articular cartilage

Is unwanted removal of material from solid surfaces by mechanical action.

Holding a static yoga posture is an example of what type of exercise?

Isometric

Aging causes

Reduction in strength

Summation

Mechanical responses to successive stimuli added to initial response

A second-degree sprain has the following symptoms except

Moderate pain

•Thenar eminence

Mound on radial side of the palm formed by intrinsic muscles acting on the thumb

After successful surgery and months of rehabilitation, Corey has been medically cleared to ski again. Again, she strikes a tree stump and loses her balance, but this time she is skiing much slower and her body is able to prepare for impact. Explain the biomechanics of how her triceps surae (calf) muscles are able protect her tibia from re-fracture.

Muscles are very important in body and joint stability. Muscles are able to contract and either shorten or lengthen in order to help provide stability, and prevent injury. In this case, the calf muscles most likely contracted, which would pull on the tibia and fibula, preventing the tibia from forcefully colliding with the boot and ultimately prevent refracture. Also, it was very important that she was skiing slower this time, because this allowed more time for the contraction of the muscles, and the longer the contraction, the greater the force generated.

-Cortical (or compact) bone

Outer shell of high density

In the three-component model of muscle, which component most closely corresponds to the connective tissue sheaths?

Parallel elastic component

Briefly explain, in an equation format, which components contribute to the (1) passive, (2) active, and (3) total length-tension curves.

Passive=PEC Active=SEC+CC Total=PEC+SEC+CC

For the average American, which of the following does not help maintain bone integrity?

Putting as little stress on the bones as possible

In the three-component model of muscle, which component most closely corresponds to the tendon?

Series elastic component

Label components A-D on the below drawing of the Hill Mechanical Model of Muscle for a single musculotendinous unit.

Springs(series elastic component), parallel damper(contractile component), Parallel spring(parallel-elastic component)

Which phrase best defines biomechanics?

The study of the structure and function of biologic systems by means of the methods of mechanics

Discuss where the two types of bone are found in a long bone and why.

The two types of bone are cancellous and cortical. Cortical bone is found on the edge of the bone and is very strong. Cancellous bone is typically found inside the ends of long bone. This is positioned here because the cancellous bone isn't as strong and its function is to absorb more energy. So, it isn't on the outside because it would not be strong enough to support the direct contact and loading from other bones, but it is there to absorb energy from the loads. That is why cortical bone is on the outside to ensure strength from this direct contact.

Corey is a 24-year-old who enjoys downhill skiing. While skiing downhill at a high velocity, she strikes a snow-covered tree stump which causes her to lose her balance and wipe out. She is in intense pain and is taken to the hospital where she is diagnosed with a tibial fracture. 25(a): Describe the mechanism of injury and how it relates to bone loading properties and injury biomechanics. Be sure to mention the likely location of the fracture.

This injury is likely due to three point bending. When skiing, and coming to an abrupt stop, the inertia of the body wants to continue moving forward, causing the tibia to hit the top of the boot with high force, causing a moment, and then there will be an equal and opposite moment by the heel. This bending of the bone, and contact of the boot against the tibia will likely cause the fracture to be right at the top of the boot. Another reason why this injury would occur is because the force or load being applied to the bone is not in the longitudinal direction. As mentioned earlier, bone is strongest under compression, but most importantly, longitudinal compression. This load is being applied transversely to the bone, which results in weaker properties which therefore allow the bone to fracture.

What type of test is shown below? Which parameters change and which are held constant? (deformation vs time graph, increases then stabilizes)

This test shows a creep phenomenon test. This test is when a constant load is applied to the material, showing a quick initial increase in deformation, which then eventually slows down. So, the load is kept constant over time, and then the deformation is changing over time.

t/f Crimp is an important characteristic of the collagen fibril.

True

t/f Tendons, ligaments, and joint capsules play a critical role in motor control.

True

The distal interphalangeal joint is the articulation between which bones?

Two phalangeal bones

Vertical displacement of COM

When viewed from the side, the head "bobs" up and down 5cm. The COM movement follows 2 sinusoidal wave patterns per gait cycle (up down, up down). Maximum height occurs during midstance, and minimum height occurs during each double limb support phase.

Examples of precision grip include

Writing. Putting in contact lenses. Using a key to unlock a door.

21(d): Given the relationship between load and repetition as it relates to fatigue injury in bone below, what do zone A and line B represent? Identify where you would be on the graph if you sustained a stress fracture from jogging and explain why. (load vs repetition graph, curve starting high going low, A under and B over)

Zone A represents the safe zone for bone injury. At any point under the curve, the load-repetition correlation would be low enough to avoid injury. Line B is the line where injury would occur. At a specific point on the line, there is a corresponding load and amount of repetition that would lead to injury. If you were to get a stress fracture from jogging, it would occur toward the right of curve B. That is because jogging isn't a super high impact or high load activity, but the repetitions are much higher. So if a stress fracture were to occur, it would be at high repetitions and a lower load.

Osteoarthritis has been shown to have a relationship to

abnormal ECM remodeling by chondrocytes and loosening of collagen network

cam deformity femoroacetabular impingement

abnormal bone/ extra bone of femoral neck

pincer deformity femoroacetabular impingement

abnormal/extra bone of acetabulum

An extensor mechanism injury may be characterized by

abnormally high tensile loads placed on the patella

When setting up equations from a static free-body diagram of the hip in the frontal plane, it is appropriate to set the abduction moments equal to the ______ moments.

adduction

The following factors affect the biomechanical properties of tendons and ligaments except (Immobilization Previous Injury, None of the above, All of the above affect the biomechanical properties of tendons and ligaments, Aging, Pregnancy)

all the above

Muscle fibers contract in

all-or-nothing fashion

Which of the following is not an example of a vector quantity? (Velocity, Force, Acceleration, Angle)

angle

torsion angles: retroversion

angle < 12 degrees, can lead to toeing in and out

torsion angles: anteversion

angle > 12 degrees, can lead to toeing in and out

Which term best describes this statement: "The behavior of bone will vary with the direction of the load application?"

anisotropic

water most concentrated near

articular surface

Sliding and rolling occur at the knee contact point to

avoid impingement, prevent the femur from rolling off the tibia plateau

Distal

away from the point of attachment

Posterior

back, dorsal

Viscoelastic materials exhibit a stress-strain relationship that is

both linear and nonlinear

collagen Network is dominated

by type I fibers ~60% -Other types (e. g., III, IV, V, VI) are also present

Once the action potential reaches the muscle fibers, what type of ions are released into the area surrounding the myofibrils?

calcium

Creep phenonmenon

can be applied to treat soft-tissue deformities

Holding the hand in a fixed position and drawing an imaginary O in the air with the thumb is best described as

circumduction

Biomechanics concerns the application of

classical mechanics to the analysis of biologic and physiologic systems.

•All three joints never

close packed at the same time

Bone tissue is composed primarily of what type of fiber?

collagen

Alice presents with decreased subtalar range of motion. You would anticipate she would

compensate with her talocrural joint.

bone is strongest and stiffest in

compression

coracoclavicular ligaments

conoid: reinforces the joint up and down trapezoid: reinforces it horizontally acromioclavicular: holding joint together and stabilizing

The right and left deltoid muscles are _____ to one another.

contralateral

What are the two types of bone tissue?

cortical and cancellous

Low loading rate

crack bone

Yielding in bone (compression) is indicated by

cracking of the osteons or interstitial lamellae

Yielding in bone (tension) is caused by

debonding of the osteons at the cement lines and microfracture

The quadriceps force _______if you lean forward before rising from a chair.

decreases

The 4-bar linkage model

describes the anterior and posterior stability

During which type of contraction is the greatest muscle force possible?

eccentric

stress-strain E

elastic limit: point at which if you remove the strain it will not come back

stress strain bone: continued loading

eventual fracture

Elastin provides

extensibility

Which action occurs about the ulnohumeral joint?

extension

Hip capsule ligaments are tightest in which joint position?

extension and internal rotation

High loading rate

extensive damage bone

If the plastic region is surpassed, what occurs?

failure

Tendons and ligaments undergo deformation before

failure

In cortical bone, fibers are typically arranged in what configuration(s)?

longitudinal, circumferential, oblique

Fracture categories:

low-energy (skiing), high-energy (car accident), very high-energy (gunshot)

Depression scapula

lowering the scapula

movements of knee

mainly flexion and extension, some internal and external rotation. (flexion, little internal rotation) (extension, more external rotation). Roll and slide motion of knee

Which type of athlete is most likely to have the highest concentration of type I muscle fibers?

marathoner

Protraction scapula

move scapulae apart

Retraction scapula

move scapulae together

Endomysium surrounds

muscle fiber

Structural unit is

muscle fiber

The symptom of chronic pain in those with tendonitis is a result of

neurovascular in-growth

does cartilage have good healing capacity

no, poor healing

compression fracture pattern

oblique

Midstance

occurs immediately before terminal stance.

Co-activation of agonist-antagonist muscles

occurs when a joint may be reversing direction.

Contralateral

on opposite sides

Muscle hypertrophies with

physical training

Standing on one's toes is an example of

plantarflexion

Supination is composed of which joint motions?

plantarflexion, inversion, adduction

All of the following are functions of cartilage except (Reduce Friction Improve joint congruency, Increase joint stability, Produce joint motion, Increase load distribution area)

produce joint motion

what muscle group predominates knee movement

quadriceps

Which type of analysis is a nonnumeric evaluation of motion based on direct observation?

qualitative

Using a force platform to measure the forces imposed on the feet during walking is an example of what type of analysis?

quantitative

Forearm pronation occurs about the _____ joint.

radioulnar

The carrying angle of the elbow

ranges from 10-25 degrees.

Muscle trophism is restored through

remobilization.

Downward rotation scapula

return to normal

Which of the following is not one of the four properties of skeletal muscle tissue?

reversibility

When flexing the knee, there is a small but significant amount of

rotation

Wear on articular cartilage can cause

rough spots on the cartilage and osteoarthritis

What is the best exercise for bone to promote Wolff's Law? (Cycling, Running, Snowboarding, Swimming)

running

stress-strain R

rupture/failure point: material fails

A somersault occurs in which plane?

sagittal

patellofemoral joint main plane of motion

sagittal

what plane accounts for nearly all motion of the knee

sagittal plane

The _____ is the smallest contractile unit of muscle.

sarcomere

•2nd Degree sprain ligament injuries

severe pain, some joint instability; progressive failure of the collagen fibers, partial ligament rupture; possible joint instability

A ____ lever arm length of the abductor muscle occurs with coxa valga.

shorter

A closed reduction maneuver is applied to restore positioning and reduce pain if you have a

shoulder dislocation

hip JRF = 3 times BW during

single leg stance

Osteoblasts

single nucleus, produce a new bone called osteoid;responsible for the calcification of the bone

torsion fracture pattern

spiral crack

Select the term that best describes the branch of mechanics that examines systems that are not moving or are moving at a constant speed.

statics

Collagen gives

strength and flexibility

21(a): What are the 3 most important mechanical properties of bone?

strength, stiffness, toughness

A relative reference frame is one in which the movement of a segment is described relative to

the adjacent segment

Ligaments are different from tendons in that

the collagen fibers are not parallel.

Biomechanics aims to improve

the knowledge of the human body.

Studies in biomechanics determine

the mechanical properties of biologic materials (bone, muscle, etc.).

I band:

thin filaments and elastic titin

Medial

toward midline of the body

Inferior

toward the bottom of the feet

Proximal

toward the point of attachment

Superior

toward the top of the head

Bone is strongest and stiffest in compression

true

side to side displacement of COM

varies 2 cm right and left for a total of 4 cm

Isokinetic is a term used to refer to an exercise performed at a controlled _____ with varying resistance.

velocity

The anteroposterior axis runs

ventral and dorsal

Which is not a way that muscle attaches to bone?

via a sarcolemma

______ is the most abundant component of cartilage.

water

most abundant component of cartilage

water

walking base

width of step

A close packed position of the midfoot occurs

with subtalar supination to provide a rigid lever for push-off.

bending fracture pattern

y shaped crack

stress-strain y

yield point: add more strain start to see reduced stress capacity

Scapulothoracic Articulation

•"Joint" between the scapula and the thorax •Gliding of the scapula occurs on the posterior aspect of the thorax

Case Study 13-1: Elbow Fracture Dislocation

•16 year old male gymnast •Fall on outstretched arm •Axial loading resulted in radial head fracture, that altered joint congruency and elbow stability •Radial head posterolateral dislocation with ulna supination on humeral -LUCL injury -RCL injury Capsule injury

•Injury mechanisms are similar for ligaments and tendons

•2 Categories or both -High levels of stress or load (external violence) -High rates of strain (overuse injury) -High levels of stress and strain (contact-collision sport injury)

Case Study 12-2: Shoulder Instability

•21 year old man fell while skiing •Fell on right UE causing forceful abduction and external rotation •Acute pain and unable to move his arm •Loss of the normal contour and painful ROM •Anterior dislocation with posterior superior humeral head impaction fracture and detachment of the anterior labrum •Shoulder instability resulted from structural alteration of bony geometry, ligaments and labrum •Subsequent dislocation, operative treatment and rehab

Case Study 2-2: Fatigue Fracture

•21 year old military recruit running 60 yards with recruit on his back •Fatigue fracture in L femur •Intensity of load •Muscle fatigue •Low repetition •Lead to tensile microdamage

Case Study 2-3: Bone Overloading

•23 year old military recruit •Intensive heavy physical training with repetitive continuous crawling in awkward position for several weeks •High repetitions •High frequency of loading>bone remodeling •Muscle fatigue •Oblique fracture of femor

Case Study 4-1: ACL Failure

•25 year old male •Recreational soccer athlete •ACL injury from abnormally high rotational torque on the knee •Strain deformation lead to high internal stress and complete ACL rupture •Abnormal joint motion and contact stress -Decreased stability -Degenerative joint disease

Case Study 14-1: Carpal Tunnel Syndrome

•26 year old female administrative assistant •Right hand and wrist discomfort and progressive severity •Worsen with prolonged hours of typing and mousing •Numbness, tingling, swelling, grip weakness •Compression of median nerve and CTS due to repetitive loading with sustained and awkward wrist positions •Underwent CTS release surgery

Case Study 12-1: Separated Shoulder

•26 year old soccer player •Tripped and landed directly on R shoulder •Pain at the AC joint, swelling, and noticeable prominence. •Dislocation of the AC joint -Clavicular end displaced superiorly 100% •Due to disruption of static stabilizers (acromioclavicular and coracoclavicular ligaments)

Hip Capsule Provide Stabilization

•3 capsular ligaments -2 anterior -1 posterior •Provides stability, especially in extreme ranges of motion •Tightest in extension and medial rotation of the hip joint, from coiling the ligaments •Loosest in flexion and lateral rotation •Can provide insight to dislocation

boot top fracture

•3-point bending fracture •Bending moment acted on proximal tibia as skier fell forward over the top of the boot •Equal moment produced by the fixed foot and ski acted on distal tibia

Case Study - Extensor Mechanism Injury

•30 year old basketball player •Forceful knee flexion during jump landing •Strong quadriceps eccentric contraction produced abnormally high tensile loads on the patella •Patella fracture -Quadriceps force > bone strength •Decreased dynamic stability •Lack of extension function necessary for gait, stair climbing, sit to stand

Case Study - ACL Injury

•30 year old male •Downhill skiing •Internal tibial rotation trauma in right knee •Anterior positive drawer test, positive Lachman test, positive pivot shift test •Treatment objectives -Prevention of reinjury •PT •Instability •Surgery 10 months post injury

Case Study 2-1

•4-point bending •Refracture at its weakest point, the original fracture site

Case Study 3-1: Knee Meniscectomy

•40 year old male •Knee pain, swelling, limited ROM •Joint surface incongruity •Small contact area •High contact pressure •Microscopic stress concentrations leading to damage

Case Study 4-2: de Quervain Tenosynovitis

•45 year old female •Graphic designer •Wrist pain •Abductor pollicis longus and extensor pollicis brevis tendons affected •Repetitive strain injury -High repetition, low force (high strain rate) -Molecular displacement and deformation -Many contributing factors

Case Study 13-2: Tennis Elbow (Lateral Epicondylitis)

•57 year old woman, avid tennis player •Gradual onset of pain •High strain rate resulting in repetitive microtraumas •Overuse injury in tendons on the lateral epicondyle •PT and ultimate surgical repair of extensor carpi radialis brevis muscles •Lateral epicondylitis is up to 10 times more likely than medial epicondylitis

Case study: Gait Adaptation in ACL Deficiency

•60 year-old male •Partial tear of right ACL 10 years ago •No surgical repair •Trouble descending stairs •Reduction of support phase peak knee flexion and knee extensor moment •Quadriceps avoidance gait pattern

Case Study 12-3: Subacromial Impingement Syndrome and Rotator Cuff Tear

•63 year old female presents with R shoulder pain for 6 mos. •Pain with overhead activities of daily living •Painful forward elevation above 60° and limited internal rotation •Subacromial impingement and rotator cuff tear of supraspinatus

Case Study 8-2: Fatigue Fracture of the Hip

•64 year-old •Femoral neck fracture •Marathon runner •Extensive change of training program •High repetitive loading, muscle fatigue, and change in loading pattern caused fracture

Case Study 3-2: Osteoarthritis

•70 year old woman •Pain, decreased ROM, joint deformity, abnormal gait •Decreased joint space •Changes in bone surfaces •Erosive cartilage lesions, cartilage loss

Case Study 8-1 Femoral Intertrochanteric Fractures

•80 year old woman •Fall from standing position •Sharp pain •Inability to stand or walk •Due to large compressive forces at the femoral neck and reduced bone strength and stiffness with aging

Needle Electrodes

•A hypodermic needle is used, which contains an insulated central conductor •Records the EMG signal from a very local area within the muscle into which it is inserted, usually only a single motor unit

Sliding Filament Theory

•A.F. Huxley •Seeks to explain production of tension in the muscle •Myosin and actin -Create cross-bridges -Slide past one another -Cause the sarcomere to contract -Active shortening of the muscle -Results from relative movement of actin and myosin filaments past one another -Force of contraction developed by myosin heads movement in contact with actin filaments -Troponin and tropomyosin regulate contact between filaments -Calcium ion turns contractile activity on and off

Acetabulum and labrum

•Acetabulum with the labrum •Transverse acetabular ligament •Labral tissue is mainly fibrocartilage •Labrum provides stability and congruity -Vacuum produced by acetabular fossa

Muscle-Tendon Unit

•Acts a dynamic restraint •Allow muscles to be pre-positioned at an optimal distance from joints without the need for increased muscular length

Function of the Patella

•Aids knee extension: -By lengthening lever arm of quadriceps muscle -This occurs throughout entire range of motion -This allows wider distribution of compressive stress on femur

Tendinopathy

•All conditions related to tendon pathology Due to high rates of strain

Role of Knee Ligaments ACL

•Anterior cruciate ligament (ACL) originates on the medial wall of the lateral femoral condyle and inserts into the tibial plateau where it blends with the anterior horn of the lateral meniscus. •These attachments allow it to resist anterior translation of the tibia, in relation to the femur. •ACL strain or tear occurs during lateral rotational movements in sports or falling back.

Four Major Muscle Groups

•Anterior flexors •Posterior extensors •Lateral extensor-supinators •Medial flexor-pronators

Effect of Skeletal Muscle Architecture

•Arrangement of contractile components affect contractile properties •The more sarcomeres in series, the longer the myofibril •The more sarcomere in parallel, the larger the CSA of the myofibril

Strain Rate Dependency in Bone: Viscoelasticity

•Behavior varies with the rate at which it is loaded •Bone is stiffer and sustains a higher load to failure when loads are applied at higher rates •Bone stores more energy before failure at higher loading rates •Strain rate increases as activities become more strenuous

Sit to Stand and Toilet Transfers

•Bending forward reduces the moment due to the body weight at the knee •Therefore, the quadriceps can generate less force when a person leans forward before standing up •Raised seat reduces moment of body weight at knee •Recommended: try the below examples using approach from previous slide, and see if you get the same quadriceps force

Torsional Fracture of Canine Femur

•Bone fails first in shear •Formation of initial crack parallel to the neutral axis of the bone •Second crack forms along plane of maximal tensile stress

Young and Old Tibia Tested in Tension

•Bone strength comparable •Old bone is more brittle •Old bone has lost its ability to deform

fiber organization multipennate

•Both varieties •Deltoid

Tensile Fracture of Calcaneous

•Contraction of triceps surae muscle during tennis match •Bone is weaker in tension than in compression •Fractures produced by tensile loading are typically in bones with a large proportion of cancellous bone

Influence of Muscle Activity

•Daily activities induce different loads. •Fractures are due to a combination of loads. •Muscle contraction affects stress patterns: -Producing compressive stress -Neutralizing tensile stress

4-Bar Linkage Model

•Describes function of the cruciate ligaments -ACL -PCL •Assumes single plane and constant length throughout motion •Predicts the knee contact point will move posteriorly with knee flexion •Shows how the cruciates provide anterior and posterior stability

•Compression testing

•Difference in mechanical behavior for two bone structures •Trabecular bone has a substantially greater modulus of toughness (area under curve) than cortical bone

Osteoarthritis

•Disruption of collagen network is a key factor in the initial events leading to development of OA •Swelling is due to the loosening of the collagen network, hence the water content of OA cartilage

Femoroacetabular Impingement

•Due to bone of the femoral neck abutting the acetabulum •Impingement caused by structural deformities are the most common cause of osteoarthritis (Maheshwari et al. 2007)

loading on bone

•During standing or stance phase, bending force applied to femoral neck creates a large compressive force on the inferior neck and tensile force on the superior neck •If the gluteus medius contracts, the compressive force increases, and the tensile force decreases •This reduce injury potential because injury is more likely to occur in tension

Isometric Contractions

•Energy-expending process in which the length of the muscle fibers does not change •The muscle neither lengthens nor shortens to produce force •Squeeze a sealed bottle or can, now squeeze it harder

Eccentric Contractions

•Energy-expending process that results in lengthening of the muscle fibers •An eccentric contraction occurs when the muscle lengthens while contracted (or under the influence of the load) •Greatest force generating contraction •Common examples are lowering or slowing motions •Protect the joint from damage by forced, rapid motion •The biceps eccentrically contracts to lower a load in the hands (when we are upright against gravity)

Concentric Contractions

•Energy-expending process that results in shortening of the muscle fibers •When a muscle shortens as it contracts •We clearly see and feel this when we lift a weight and watch our biceps pump up and shorten. This is a concentric contraction.

•Chronic tendonitis

•Evidence of neurovascular in-growth -Chronic pain -Attempt of tendon to heal but also has nerve growth

Composition and Structure of Skeletal Muscle (continued)

•Fibers composed of myofibrils •Myofibrils aligned to create band pattern •Each repeat of pattern = sarcomere •Myofibrils composed of: -Thin, light filaments of actin -Thick, dark filaments of myosin •Intramyofibrillar cytoskeleton made of titin and nebulin

cartilage

•Firm, flexible tissue -1-7 mm thick •No blood supply or nerves •Nourished by fluid within the joint

Surface Electrodes

•Fixed to the skin over the muscle •The EMG being recorded as the voltage difference between two electrodes •The EMG signal picked up by surface electrodes is the sum of the muscle action potentials from many motor units within the most superficial muscle or muscles -25 mm of the skin surface •Superficial muscles are ideal -Cross-talk may still occur Not suitable for deep muscles

during gait Hip joint motion in 3 planes:

•Flexion-extension •Adduction-abduction •Internal-external rotation

Hip ROM in 3D

•Flexion: 0°-140° •Extension: 0°-15° •Abduction: 0°-30° •Adduction: 0°-25° •External rotation: 0°-90° •Internal rotation: 0°-70°

•Activity of shoulder muscles determined during Scapulothoracic motion

•Force couple

Force-Velocity of Concentric Muscle

•Force decreases with increased velocity •Fewer cross-bridges can be maintained at higher velocities •Maximum tension in isometric (v=0) condition -Many cross-bridges •Maximum power generated in concentric muscle action with velocity and force at 30% max

Force Production in Muscle (contraction)

•Force produced in muscle increased with: -Prestretching -Increase in muscle temperature •Energy for contraction and release comes from ATP •Muscle fatigue occurs when synthesis of ATP is insufficient to keep up with ATP breakdown

•Cyclic loading

•Fracture resulting from repeated loading is called fatigue •Used for testing implants, prostheses, or fixation devices

motor unit

•Functional unit of skeletal muscle -Single motor neuron -Muscle fibers innervated by motor unit (4 - 2000) •Smallest part of the muscle that can be made to contract independently •All or none response •Recruitment: firing of additional motor units in response to great stimulation of the motor nerve •Group of muscles innervated by the same motor neuron •Action potential -Signal to contract from motor neuron •Neuromuscular junction -Also called end plate -Where action potential from neuron meets the muscle fiber •Conduction velocity -Velocity at which action potential is propagated along the membrane

Once collagen-PG matrix is disrupted it can induce:

•Further disruption of collagen-PG matrix due to repetitive matrix stressing •Increased "washing out" of PGs due to violent fluid movement and thus impairment of articular cartilage's interstitial fluid load support capacity •Gross alteration of normal load carriage mechanism in cartilage, thus increasing frictional shear loading on the articular surface

Collagen

•Gives a layered character to cartilage

Tibiofibular Joint of the Knee

•Gliding joint •Accepts 16% of the load of the leg •Absorb and controls tensile stress

Fibrocartilage Functions

•Improves fit between the bones •Intermediary between hyaline cartilage and other connective tissues

Pennation Angle

•Influences force production -Larger fascicle angle results in greater PCSA and greater force production -Larger fascicle angle results in muscle operation closer to that fiber length that allows maximal force production (L-T curve) -Larger fascicle angle results in shortening of the fibers. This increases force by the F-V relationship, by decreasing velocity, v=d/t •Slower contraction = greater force production

•Activity of shoulder muscles determined during External rotation

•Infraspinatus •(Posterior deltoid and teres minor)

instant center technique

•Instantaneous center of motion (v=0) •Used to describe surface joint motion •In sagittal plane instant center follows a curved pathway: -It reflects changing femoral radii of curvature (semicircular) •Displacements of tibiofemoral contact point tangential to tibial surface: -Sliding occurs throughout range of motion: •Medial side: sliding motion only •Lateral side: combination of rolling and sliding

Fine Wire Electrodes

•Intramuscular recordings •Thumb-screw connection to fine-wire •Insulated, hooked wires with 200mm tail with 6mm bare-wire terminations •EMG signal recorded between a pair of wires inserted using a single needle •Less interference from movement and from electromagnetic fields Invasive, uncomfortable or painful

Stability of the Knee Joint

•Key to healthy knee joint •Occurs in all planes •Static stability -Provided by the ossesous configuration, menisci, ligaments and capsule •Dynamic stability -Muscles surrounding the knee

Proteoglycan

•Large protein-polysaccharide molecule •Adds stability and rigidity to ECM

Knee Menisci and Ligaments

•Lateral and medial menisci •Anterior and posterior cruciate ligaments (ACL and PCL) •Transverse ligament •Medial and lateral collateral ligaments

Eccentric Examples

•Lowering from a sit up is eccentric for the abdominal muscles •Lowering into a chair is eccentric hip flexion -What would happen if your hip flexors fired? •Lowering a load to the floor is eccentric for your back extensors

•Magnitude of JRF acting on hip influenced by:

•Magnitude of JRF acting on hip influenced by:

wrist and fingers functions

•Manipulation activities •Very fine movements •Many stable, yet mobile, segments

shear fractures bone

•Most often seen in cancellous bone •Shear stress is greatest when the angle of applied force is equal to 45°, where it has a value that is half that of the maximum normal stress

instant center technique formula

•Movement •s=r(theta) -s is the distance, r is the radius to the instant center, and θ is the range of flexion in radians •Sliding and rolling must occur to avoid impingement or femur from rolling off tibia plateau

Motion Analysis Methods gait

•Multiple cameras measure positions of reflective markers •Force plates measure ground reaction forces and moments •EMGs measure muscle activity •Kinematics (motions) and kinetics (forces) computed •Data is synchronized

Reference Systems

•Necessary for accurate observation and description •Fundamental and anatomical positions

•Qualitative

•Non-numerical •Based on direct observation •Equipment not necessary •Focus on time and space •Examples: -Rotation of femur during golf swing -Adduction of humerus during freestyle swim

Quantitative

•Numerical •Based on data collected •Equipment necessary •Focus on forces •Examples: -Stress on shoulder during baseball pitch Compression force on

Meniscus Tears

•Occur with a sudden changes of direction with the weight all on one limb •The resultant compression and tension on the meniscus tear the fibrocartilage •No pain •Peripheral attachment sites are the site of irritation and sensitivity

cortical bone density

•Very dense with a porosity <15% -Small changes in porosity lead to significant changes in stiffness and strength of bone

Screw-home mechanism

•Occurs in the tibiofemoral joint in extension •Adds stability to knee joint in full extension •Additional passive stability given by: -Ligamentous structures -Menisci •Dynamic stability given by: -Muscles surrounding the knee

fiber organization bipennate

•Off both sides of tendon •Gastrocnemius

fiber organization unipennate

•Off one side of tendon •Semimembranosus

•Activity of shoulder muscles determined during Extension

•Posterior deltoid •Middle deltoid

Force-Velocity Relationship

•Relationship between force and velocity in eccentric muscle action is opposite to that of concentric muscle action.

Osteoporosis

•Resorption exceeds deposition •Increases the risk of fracture •Related to -Hormonal factors (i.e., menopause) -Nutritional imbalances (i.e., calcium intake) -Lack of exercise

stress fractures

•Resorption weakens the bone •Deposition occurs too slowly •Results from -Repetitive muscle forces pulling on the bone -Muscle fatigue à reduced shock absorption •10% of injuries to athletes

Limitations of EMG

•Semi-quantitative technique •Gives little indication of the strength of contraction of individual muscles •Difficult to obtain satisfactory recordings from a walking subject -Electronic characteristics of the equipment -Skill of the operator in selecting the recording sites and attaching the electrodes to minimize skin resistance and movement artifacts

Compression Fracture of Human First Lumbar Vertebra

•Shortens and widens •Fractures are often in elderly with osteoporotic bone tissue

cancellous bone

•Spongy bone interior to cortical bone •Found in the ends of the long bones, in the body of the vertebrae, and in the scapulae and pelvis •Lattice-like structure

canaliculi

•Spread from the lacunae of an osteon, connecting osteocytes to one another •Crack in the interstitial lamellae between osteons

Bone Testing with MTS Machine

•Strain is measured with a strain gauge •Stress calculated from the total load measured •Young's modulus E = σ/ε

bending bone

•Stresses are highest at the periphery and lowest near the neutral axis •Tensile and compressive stresses are unequal because the bone is asymmetric

•Activity of shoulder muscles determined during Internal rotation

•Subscapularis •(Sternal head of pec major, lats and teres major)

Summation

•Summation of contraction in a muscle held at a constant length. •The resulting peak tension in summation is greater than that of a single twitch. •Smooth summated curve translates to smooth movement

•Activity of shoulder muscles determined during Forward elevation in scapular plane

•Supraspinatus •Deltoid

Methods of EMG Recording

•Surface electrodes •Fine wire electrodes •Needle electrodes

Healing of Tendons and Ligaments and Grafts

•Tendons and ligaments remodel in response to mechanical demands •Grafts are useful in ligament reconstruction •Tendons and ligaments do not return to normal levels

Force-Time Relationship

•Tension (force) generated by a muscle is proportional to the contraction time -The longer the contraction time the greater the force -Slower contraction = greater force •More effective force transmission to tendon

Injury Potential knee

•The knee joint is a frequently injured area of the body, accounting for 25% to 70% of reported injuries depending on the sport •Often related to poor conditioning and/or alignment problems in the lower extremities •Running exerts forces of 3× BW on the knee with a frequency of 1,500 contacts per mile •Traumatic injuries usually involve knee ligaments caused by forceful twisting action -ACL is the most common ligament injured -Torn menisci can also result from twisting

Role of Knee Ligaments PCL

•The posterior cruciate ligament (or PCL) connects the posterior intercondylar area of the tibia to the medial condyle of the femur. •PCL resists posterior tibia translation. •PCL injury results from direct blow to a flexed knee (e.g. hitting knee on dashboard during an accident, falling on flexed knee)

A.V. Hill Mechanical Model of Muscle

•Three-component model -Contractile (CC) •Converts stimulation into force •Models the contractile proteins (actin, myosin) -Parallel elastic (PEC) •Allows the muscle to be stretched •Associated with fascia surrounding the muscle •Models the epimysium, perimysium, endomysium, and sarcolemma -Series elastic (SEC) •Transfers muscle force to the bone •Models the tendon

knee kinetics

•Tibiofemoral and patellofemoral joints subjected to high forces •Forces from muscles have greatest influence -Quadriceps •Knee compressive force ranges between 2 and 4 BW •Higher flexion activities = highest forces Medial side carries higher forces than lateral

Viscoelastic Behavior

•Time-dependent •Properties change with different rates of loading •Greater stiffness at higher strain rates -Store more energy -Require more force to rupture -Undergo greater elongation •Stress-strain curves moves to the right with loading cycles -Permanent deformation is progressively greater with every loading cycle -Plastic component •Increase in elastic stiffness as repetitive loading progresses -Microfailure can occur in physiologic range

Role of Articular Cartilage

•Transmit compressive forces across the joint •Allows motion in the joint with minimal friction and wear •Redistributes contact stresses over a larger area •Protects the underlying bone

Drawer Test

•Used to test rupture of cruciate ligaments •The examiner sits on the patient's feet and grasps the patient's tibia -Pulls it forward (anterior drawer test) or backward (posterior drawer test) •Test is positive if knee moves excessively in either direction -Positive anterior test: likely ACL tear -Positive posterior test: likely PCL tear

Do these contractions ever occur alone?

•Yes, sometimes... but mostly no •When you lift or lower a weight you use muscles on one side of your body •Many other muscles also provide stability or co-contract while you concentrically, eccentrically or isometrically perform a task

Series of lamellae form an

•an osteon or Haversian system -Weight bearing pillars oriented parallel to the stresses

Lateral

•away from midline of the body

Upward rotation scapula

•bottom of the scapula moves away from the trunk, top moves toward

cancellous vs cortical turnover rate

•cancellous has higher turnover rate than cortical bone with more remodeling along the lines of stress

M line:

•connects adjacent thick filaments in the center of the H zone

A bands:

•dark bands in central region composed of thick filaments

Z line

•defines the ends of the sarcomeres; short thin filaments attach here

Muscle atrophies with

•disuse and immobilization.

Perimysium surrounds

•fascicle (several muscle fibers)

During scapular motion the subscapularis muscle

•glides on the serratus anterior muscle •These muscles stabilize the scapula and prevent "winging"

Intrinsic material properties and resistance to flow of solid matrix define

•interstitial fluid pressurization.

Bone exhibits more brittle or more ductile behavior depending on

•its age and rate at which it is loaded -Younger bone is more ductile -Bone is more brittle at a higher loading rate

EMG is the

•measurement of the electrical activity of a contracting muscle -Muscle action potential •Provides information on the timing of muscular contractions

Bone fundamental structure

•osteon Aka haversian system

If one has decreased ankle range of motion, they will present with the clinical compensation of

•out-toeing. -Allows for the motion required for walking to occur at the subtalar joint -This occurs because the greatest motion will always occur about the axis that is closet to perpendicular to the plane of progression •In this case, that would be the subtalar joint •The ankle joint is less perpendicular to the plane of progression than normal -Ultimately, could lead to secondary degenerative arthritis

Elevation scapula

•raising the scapula (shrug)

Defects can greatly

•weaken the bone -Torsion

Dynamics Equations

•ΣF = 0 •ΣM = 0 •F=ma •M=Fd •T=Iα •Concepts of vector addition, free body diagrams, forces, moments