Biomechanics Exam 2 Review

Excitation Contraction Coupling

- Action potential occurs on a motor axon - Releasing of acetylcholine at NM junction - Na and K get released at motor end plate causing end plate potential - Depolarization occurs releasing Ca - Ca binds to troponin - Tropomyosin moves out of the way on the actin filament - Actin and Myosin start sliding past each other

Load of acetabulum → when femoral head is being loaded inside of it

- Concave surface - Unloaded acetabulum is smaller in diameter than femoral head - Loaded acetabulum deforms about the femoral head from elastic deformation - Load is anterior, superior, posterior

During swing phase of gait the knee is experiencing what in terms of convex/concave rule?

- Convex (moving) on concave - During the swing phase of gait the knee flexes to 60 degrees

Know about increased temperature and muscle and what is its effect?

- Increase temperature increases conduction velocity across the sarcolemma - Increases frequency of action potentials and more muscle force is produced - Low temperatures, show less shortening velocity and less isometric tension - Warming up, getting loose, increase blood flow

tibiofemoral shaft angle

- Line through central part of patella - Line though tibial crest - Normal angle 6 deg > 6 deg Genu Valgum < 6 deg Genu Varus

MCL and LCL, What does it prevent?

- MCL (medial collateral ligament) prevent lateral rotation - LCL (lateral collateral ligament) prevents medial rotation

Seesaw, raising up on toes, lifting a gallon of milk → what lever systems are those?

- Seesaw (first class) - Raising up on toes (second class) - Lifting a gallon of milk (third class)

What is the hindfoot comprised of?

- Tibiofibular joint: syndemosis - Talocrural joint - Subtalar joint

Patella infera

- an abnormally low patella - it most often results from to soft tissue contracture - hypotonia of quadriceps muscle following surgery or trauma to knee

Know different contractions → going from heel strike to foot flat

- just after heel strike the joint reactive forces are 2 to 3 times more than body weight and associated with contraction of hamstring for deceleration - during knee flexion in the beginning of the stance phase, the joint reactive forces was about 2 times body weight and is associated with contraction of the quads to prevent buckling of the knee - Peak joint reaction force occurs during the late stance phase just before toe-off which ranged from 2-4 times body weight, associated with contraction of the gastrocnemius - flexion and extension moments of the knee is 20-30 times larger than the moment produced in the frontal and transverse planes

Patella alta

- refers to an abnormally high patella in relation to femur; - may result in Subluxation and dislocation of patella

Screwhome mechanism → muscles involved, what muscle unscrews it

- terminal rotation of the knee; tibia externally rotates about 20 degrees on fixed femur; femur internally rotates - muscles involved: VMO muscle locks knee in place - what muscle unscrews? Popliteus muscle unscrews tibia, goes in on an angle • De-rotates → moves knee from screwhome mechanism • Not a major knee flexor but it helps b/c its right at joint level

Trendelenburg gait

- weak gluteus medius of some sort, stance leg problem → does NOT occur w/ swing leg - hip problem happens on same - trunk on opposite side is affected

Know what makes up medial longitudinal arch

1. Plantar fascia 2. Long and short plantar ligaments 3. Spring ligament or calcaneonavicular ligament

Pressure you need on heads...what heads is callus formation occurring on?

2 and 3 MT heads

Precautions of total hip

3 Contraindications • No internal rotation of problem hip • No hip flexion beyond 90 degrees → problem is also other way → still 90 degrees from trunk to hip • No crossing legs

In terms of open and closed chain movements

ACL Prevents posterior displacement of femur on tibia in closed chain movement Prevents anterior displacement of the tibia on the femur in an open chain movement PCL Prevents anterior displacement of the femur on the tibia in closed chain movement Prevents posterior displacement of the tibia on the femur in an open chain movement open chain: extension, kicking soccer ball closed chain: squat, climbing stairs

3 things of unhappy triad

ACL (anterior collateral ligament), MCL (tibial collateral) and meniscus

Plane of coxa vara and valga

Angle of inclination of neck to shaft in the frontal plane

What happens w/ rotation of femur, anteversion vs. retroversion

Anteversion: lateral tibial torsion, increase Q angle and lead to tracking of patella on femoral sulcus Retroversion: medial tibial torsion, decrease Q angle, centralizes tracking of patella

Closed packed position in knee

Closed-packed position: full extension, lateral rotation of tibia

Know about the concave/convex rule in regard to hip, knee

Concave (moving) on fixed convex → Osteo and arthro on same direction Convex (moving) on fixed concave → Osteo and arthro are in different direction Arthrokinematics (bone) Osteokinematics (knee)

Know about concentric and eccentric isometric contractions

Concentric: shortening of muscle fiber, ie biceps curl, hamstring curl, leg extension Eccentric: lengthening of muscle fibers in response to an external load, quadriceps during stair descension Isokinetic: movement of a joint is at a constant velocity, acceleration of the movement to assist in moving a load is eliminated. Quads will work concentrically to extend leg and then eccentrically to decelerate knee flexion Isometric: constant length contraction, quad sets, isometric at different angles. Less force here. Can be submaximal

Contact points of patella and knee flexion ankles

Contact area of the medial plateau is 50% larger than the lateral tibial plateau At the beginning of the motion, contact area is on the distal third of the patella As flexion approaches 90 degrees, surface contact is the proximal one half of the patella à beyond 90 degrees rotates slightly outwards

During mid-stance what muscle group contracts to slow body down?

During midstance, the calf musculature contracts to slow the body down over the foot

Know what happens w/ running regards w/ hamstring to gluteus maximus

During running, the hamstrings and G-Max are active during midstance through heel off

Ely Test (T/F)

Ely Test: Tight Rectus Femoris → crosses hip and knee → stretching out → since back stays in position → negative test • A part of his hip is going to come up as he bends it • PRONE POSITION (T/F) might say supine

Pronation movement

Eversion, Extension, Abduction

Know what happens w/ full dorsiflexion

Full dorsiflexion causes jamming of the joint (surface joint motion)

Person w/ high heels might have what problems?

Haglund's deformity i. Prominence of the posterior-superior calcaneal tuberosity can cause an overlying bursitis and Achilles tendonitis ii. Most often occurs in women and is related to shore wear with rigid heels or heel counters

Normal walking

Heel strike > foot flat: subtalar joint everts because the point of contact of the heel is lateral to the center of gravity of the ankle joint producing a valgus thrust; the forefoot pronates and becomes flexible to absorb shock and adapt to irregularities of the joint surfaces Mid-stance to Heel off: the subtalar joint inverts, supination also occurs of the forefoot causing a rigid structure allowing for propulsion

Special test that determines screw home mechanism

Helfet test - determines if the tibia rotates externally with knee extension to see if the screw home mechanism is in place

Mid stance gait → what's going w/ knee?

In terms of heel strike → 0 degrees → basically a midstance → shock absorption • As you are toeing off → toe is still there • Eventually rockets up to 60-70 degrees

femoral anteversion and what it does to patella in terms of how its positioned

Increases Q angle and leads to tracking of patella on femoral sulcus

Shape of normal knee @ instant center

Instant center → meniscus is semicircular to a certain degree

Supination movement

Inversion, Flexion, Adduction

Longer you have all the muscle contracture and how much force?

Muscle force → as you are going from flexion to extension, more force in musculature

NSAIDS

Nonsteroidal anti-inflammatory drugs

Degrees of anteversion

Normal anteversion: 12 degrees in adults Anteversion of more than 12 degrees causes internal rotation of the leg during gait to keep the femoral head within the acetabular cavity Anteversion of less than 12 degrees causes external rotation of the leg during gait

What does the assistive device go w/ somebody w/ an injured leg?

Opposite side

Know what happens w/ an overpronated foot in terms of front and back

Overly pronated foot → heel valgus

Know what happens w/ an oversupinated foot in terms of front and back

Overly supinated foot → heel varus

Classic symptoms of plantar fasciitis

Pain: Severe levels worse in the morning and after rest, pain lessens after moving around Pain is aggravated by WB all day and becomes progressively more severe Can be a dull ache or sharp Tenderness: Produced with DF of toes causing tension of the fascia Palpation causes entire plantar surface to be tender. There is tenderness in the arch more commonly as compared to the heel.

Test to check anteversion → palpation point

Palpate greater trochanter parallel to table

What extends lever arm of the quads?

Patella - Decreases the compressive stress on the femur by increasing the area of contact between the patellar tendon and femur

What tendon contributes to disability of arch of foot?

Posterior tibial tendon

1What does not belong w. foot supination?

Pronation: Eversion, Extension, Abduction

Female large Q angle

Q angle is 14 deg for males and 17 deg for females

Open packed position of knee

Resting position or loose-packed position: 25 degrees

Differences in labrums of shoulder and hip

Shoulder: glenoid labrum Hip: acetabular labrum

Tibia rotation and what happens at subtalar joint

Subtalar joint + transverse tarsal joint (talonavicular and calcaneocuboid) transforms tibial rotation into forefoot supination and pronation - Need 10-15 degrees of functional subtalar motion during gait

The menisci glide posteriorly with knee flexion and anteriorly with knee extension

T/F Question!!

Actin has 2 proteins: troponin and tropomyosin which regulate breaking and making of bonds b/w actin & myosin for muscle contraction

T/F!! True

External weight has greater leverage than the muscle force which is opposite of the second class lever

T/F!! True

This (muscle) shortening causes the Z lines to get closer, the A band stays constant

T/F!! True

Ober test

Testing ITB, stabilizes pelvis → both hips are even → if a leg is hanging up in the air → positive sign for ITB • If its dropping down → below parallel → normal IT band length

Know common lever system of body

Third class lever system (most common) - axis of rotation at one end of the bone like the second class lever - external weight has greater leverage than the muscle force which is opposite of the second class lever - most common lever class in the body. Example: elbow flexor muscles use the third class lever to produce flexion torque required to support the barbell in the figure

Hip flexor flexibility Hip test (Thomas Test)

Thomas test → hip flexors → if knee goes past table or torso (normal flexibility) • If it was tighter going up → tighter iliopsoas • Rectus femorus (attaches 2 joints, ASIS and part of the quads) → if foot was up → also positive test for tight rectus femorus o If hanging low → good flexibility

Two questions on slow twitch and fast twitch oxidative

Three fiber types: - Type I slow-twitch oxidative (SO) - Type IIA fast-twitch oxidative-glycolytic (FOG) - Type IIB fast-twitch glycolytic (FG)

Type I slow-twitch oxidative (SO)

Type I Properties: SLOW TWITCH OXIDATIVE i. slow contraction time ii. difficult to fatigue because of high rate of blood flow iii. prolonged, low intensity work iv. small in diameter, produce little tension v. red color

Which fibers are affected w/ immobilization?

Type I fibers atrophy mostly with immobilization

Type IIA fast-twitch oxidative glycolytic (FOG)

Type IIA Properties: fast-twitch oxidative-glycolytic (FOG) i. fast contraction because of high activity of myosin ATPase ii. intermediate between I and IIB because of their fast contraction and capacity for both aerobic and anaerobic activity iii. good blood supply iv. red muscle v. eventually fatigue because need for ATP overrides the supply

Type IIB fast-twitch glycolytic (FG)

Type IIB Properties (fast-twitch glycolitic (FG) i. white muscle ii. less blood supply, anaerobic iii. fatigue easily iv. large diameter, can produce great tension but for short periods of time

Know details of popliteal or baker's cysts (T/F)

a. Baker's Cyst - a type of cyst which results from egress of fluid through a normal communication of a bursa (semimembranosus or medial gastrocnemius bursa) or may be caused by herniation of the synovial membrane through the joint capsule; b. some popliteal cysts are caused by a lesion of the posterior third of the medial meniscus

Femoral head → where larger load (is it peripheral, central?)

a. Convex surface b. Articular cartilage is thickest medial-central part and thinnest at the periphery c. Small loads, peripheral concentration on the femoral head d. Larger loads, load concentration centrally, and the anterior and posterior horns

McMurray Test

a. Externally rotate tibia w/ medial force → push and straighten out knee at same time b.Clicking and pain is (positive) c. If for lateral meniscus → will internally rotate tibia and put pressure and straighten it out

When does maximal hip flexion and hip extension occur?

a. Maximal hip flexion during heel strike or initial stance phase b. Maximal hip extension during heel off c. Minimal hip abd/add/IR/ER

Know about trabeculae systems in femoral shaft

a. Medial and lateral trabeculae system is important for the amount of forces that occur at this (hip) joint b. Lateral system resists the compressive forces on the femoral head produced by the contraction of the gluteus medius, minimus and TFL c. Aging causes a degeneration of the trabeculae and cortical bone, more incidence of femoral neck fractures

Know number of what happens when you're greater or less than shaft angle

a. Normal angle is 125 degrees b. Coxa Vara: angle < 125 degrees c. Coxa Valga: angle > 125 degrees

Miserable malignment syndrome → what are the bad things from hip all the way down to foot

a. Patients who have increased femoral anteversion, genu valgum, VMO dysplasia, lateral tibial torsion, forefoot pronation b. Creates excessive lateral forces

Proper resting length to generate force

a. Resting length at 2-2.25 micrometers: maximal isometric tension across the sarcomere b. Beyond resting length, no overlap between filaments so no tension c. Shorter than resting length, less overlapping, less tension

Float phase

a. Running: double limb support disappears replaced by float phase b. Walking: double limb support: heel off one foot and heel strike on the other c. About 15%

Functional unit of a skeletal muscle

a. Sarcomere is functional unit of contractile portion in muscle b. Sarcomere a myofibril a muscle fiber a muscle c. Sarcomere Composition: i. Thin Actin filaments ii. Thick Myosin filaments iii. Elastic Titin filaments d. Related to amount of movement required: i. Fine motor units have less muscle fibers per unit ii. Gross motor units have much more fibers per unit

Where does dorsiflexion and plantarflexion happen in terms of axis?

a. Standard (if you guys stick out your foot) → putting down like you are at gas pedal b. If you put your foot down that's plantarflexion c. Lift your foot up → dorsiflexion

Deltoid ligament resists which movement?

a. Superficial and Deep Deltoid b. Both resist eversion, external rotation and PF c. Resists lateral talar shift during syndesmosis injury

In terms of hallux valgus → what happens w/ MT head in terms of being depressed

a. Toe off: the proximal phalanx passes over the MT head and depresses it b. If there is hallux valgus, MT head can not be depressed and forces are transmitted to the 2nd and 3rd MT heads causing painful plantar calluses of lesions

Understand cartilage/medial aspect of knee → in terms of is it thicker?

cartilage on medial aspect is three times thicker than laterally allowing for higher forces to occur for this adductor moment/medial moment

Another name for LCL

fibular collateral ligament

What other muscles are sprained w/ ATFL?

hamstrings

What causes kneecap to track (trap) laterally?

horizontal pull of the VMO on the patella balances the lateral pull of the rest of the quadriceps muscle - if weakness in VMO, IT band will pull laterally

Mid-stance gait in hip muscle that is related to anteversion

moment where all pressures are going towards medial aspect of knee or inner part of lower extremity - increased anteverted hip --> toe in, decreased anteverted hip --> toe out • Stronger medial trabeculae system

Definition of hallux rigidus

occurs when there is osteophyte formation at the dorsal aspect of the metatarsal head surface limiting dorsiflexion of the proximal phalanx

know what anteversion is

projection of the long axis of the femoral head and the transverse axis of the femoral condyles

What does the Thomas Heel do?

puts wedge medially to varus the heel, you would to put in opposite direction

Plane of anteversion

transverse plane

Know adductor moments and swing phase and stance phase of gait, when does it occur?

when we're heel striking, we're going from outside of foot, then in (quick?) stance, there is an adductor moment straight down the heel. • Heel strike goes lateral and then medial • Then straight down to medial plateau and medial femoral condyle • Where a lot of arthritis occurs → in medial compartment

What situation will make Anterior draw a false negative?

• Anterior draw (tests ACL) → bend knee to 90 degrees, sit on foot, basically pull and see how much translation tibia has on femur → compare it to other side o What might start contracting to help torn ACL → hamstrings → might have false negative

Anterior tibialis

• Strongest Extensors of the Foot - From heel off to heel strike → dorsiflexion so my anterior tibialis is shortening

Reverse trendelenburg gait

• gluteus medius is still problem, still stance phase but opposite of what was showed • Hip problem opposite side • Trunk problem is on ipsalateral side

Know different planes of knee

•Some frontal plane movement, transverse plane movement, coronal plane movement • Mostly sagittal plane, flexion and extension