Chapter 9 Joints

multiaxial joint: shoulder joint

- A moving bone has a relatively stationary axis of rotation that passes through the bone in a direction perpendicular to the plane of movement - Multiaxial joint: shoulder joint has three degrees of freedom or axes of rotation - Other joints are monoaxial or biaxial

tendon, ligament, bursa, and tendon sheath

- Accessory structures: 1. Tendons: strips of collagenous tissue attaching muscle to bone 2. Ligament: strip of collagenous tissue attaching one bone to another 3. Bursa: fibrous sac filled with synovial fluid, located between muscles, where tendons pass over bone, or between a bone and skin - Cushion models, helps tendons slide more easily over joints, modifies direction of tendon pull 4. Tendon sheath: elongated cylindrical bursa wrapped around a tendon - In hand and foot

articular cartilage and synovial fluid *

- Articular cartilage: layer of hyaline cartilage that covers the facing surfaces of two bones (usually 2 or mm thick) - Joint (articular) cavity: separates articular surfaces - Synovial fluid: slippery lubricant in joint cavity 1. Rich in albumin and hyaluronic acid 2. Gives it a viscous, slippery texture like raw egg whites 3. Nourishes articular cartilage and removes waste 4. Makes movement of synovial joints almost friction free

bony joints *

- Bony joint, or synostosis: an immobile joint formed when the gap between two bones ossifies, and the bones become, in effect, a single bone - Examples: 1. Left and right mandibular bones in infants 2. Cranial sutures in elderly 3. Attachment on the first rib and sternum with old age - Can occur in either fibrous or cartilaginous joint

bony joints *

- Bony joint, or synostosis: an immobile joint formed when the gap is between two bones ossifies, and the bones become, in effect, a single bone - Examples: 1. Left and right mandibular bones in infants 2. Cranial structures in elderly 3. Attachment of first rib and sternum with old age - Can occur in either fibrous or cartilaginous joint

cartilaginous joints *

- Cartilaginous joints, or amphiarthrosis: two bones are linked by cartilage - Two types of cartilaginous joints: 1. Synchondroses 2. Symphyses

third-class lever

- Effort between the resistance and the fulcrum (REF) - Most joints of the body - The efforts of a biceps curl is applied to the forearm between the elbow joint (fulcrum) and the weight in the hand (resistance)

fibrous joints

- Fibrous joint, or synarthrosis: adjacent bones are bound by collagen fibers that emerge from one bone and penetrate into the other - Three kinds of fibrous joints: 1. Sutures 2. Gomphoses 3. Syndesmoses

gomphoses *

- Gomphosis (fibrous joints): attachment of a tooth to its socket - Held in a place by fibrous periodontal ligaments - Collagen fibers attach tooth to a jawbone - Allows the tooth to move a little under the stress of chewing

first-class lever

- Has fulcrum in the middle between effort and resistance (EFR) - Atlanto- occipital joint lies between the muscles on the back of the neck (applying effort) and the weight of the face (resistance) - Loss of muscle tone occurs when you nod off in class

articular disc and miniscus *

- In a few synovial joints, fibrocartilage grows inward from the joint capsule - Articular disc forms a pad between articulating bones that crosses the entire joint capsule (Example: found in temporomandibular joint) - Meniscus: moon-shaped cartilage in knee; in each knee, menisci extend inward from left and right 1. These cartilages absorb shock and pressure 2. Guide bones across from each other and improve their fit together 3. Stabilize the joints, reducing the chances of dislocation

articular capsule

- Joint (articular) capsule: connective tissue that encloses the cavity and retains the fluid - Outer fibrous capsule: continuous with periosteum of adjoining bones - Inner, cellular, synovial membrane: composed mainly of fibroblast- like cells that secrete synovial fluid and macrophages that removes debris from the joint cavity

joints and their classification 1

- Joint (articulation): any point where two bones meet, whether or not the bones are moveable at that interface

joints and their classification 2 *

- Joint name: typically derived from the names of the bones involved (example: radioulnar joint) - Joints classified according to the manner in which the bones are found to each other - Four major joint categories: 1. Bony joints 2. Fibrous joints 3. Cartilaginous joints 4. Synovial joints

introduction

- Joints links the bones of the skeletal system, permits effective movement, and protect the softer organs. - Joints anatomy and movements will provide a foundation for the study of muscle actions.

joints and lever systems

- Long bones act as levers to enhance the speed or power of limb movements - Lever: any elongated, rigid object that rotates around a fixed point called a fulcrum - Rotation occurs when an effort applied overcomes resistance (load) at some other point (Resistance arm and effort arm are described relative to fulcrum)

supination and pronation of forearm

- Primarily forearm movements - Supination: forearm movement that turns palm to face anteriorly or upward 1. Forearm supinated in anatomical position 2. Radius is parallel to the ulna - Pronation: forearm movement that turns palm to face either posteriorly or downward - Head of radius spins - Radius crosses stationary ulna like an X

range of motion

- Range of motion (ROM): the degrees through which a joint can move 1. Aspect of joint performance 2. Physical assessment of a patient's joint flexibility

second class lever

- Resistance between fulcrum and effort (FRE) - Example: when bouncing a baby on your knee, hip is fulcrum, baby's weight is resistance, and effort is applied at the tibia

rotation of trunk and head

- Right and left rotation of trunk and head

saddle joints and plane (gliding) joints *

- Saddle joints: 1. Both bones have an articular surface that is shaped like a saddle, one concave, the other convex 2. Biaxial joints 3. Examples: trapeziometacarpal (opposable thumb), sternoclavicular joint - Plane (gliding) joints: 1. Flat articular surfaces, bones slides over each other 2. Usually biaxial joints 3. Examples: between carpal bones of wrist; between tarsal bones of the ankle; also between articular processes of vertebrae

sutures 1

- Sutures: immobile or slightly mobile fibrous joints in which short collagen fibers bind the bones of the skull to each other - Sutures can be classified as: 1. Serrate: interlocking wavy lines - Coronal, sagittal, and lambdoid sutures 2. Lap (squamous): overlapping beveled edges - Temporal and parietal bones 3. Plane (butt): straight, non-overlapping edges - Palatine processes of the maxillae

symphases

- Symphysis: two bones joined by fibrocartilage - Pubic symphysis: joins right and left pubic bones with interpubic disc - Bodies of vertebrae joined by intervertebral discs 1. Only slight movements between adjacents vertebrae 2. Collective effect of all 23 discs give spine considerable flexibility

synchondroses *

- Synchondrosis: bones joined by hyaline cartilage - Temporary joints in the epiphyseal plates in children (Bind epiphysis to diaphysis) - First rib (costal cartilage) attachment to sternum by synchondrosis (Other costal cartilages joined by sternum by synovival joints)

syndesmoses *

- Syndesmosis: a fibrous joint at which two bones are bound by long collagen fibers - Examples of a very mobile syndesmosis: interosseus membrane joining radius to ulna allowing supination and pronation - Example of a less mobile syndesmosis: joint between tibia to fibula

synovial joints or diarthrosis

- Synovial joint, or diarthrosis: joint in which two bones are separated by a joint cavity 1. Most familiar type of joint 2. Most are freely mobile 3. Most structurally complex type of joint 4. Most likely to develop painful dysfunction 5. Most important joints for physical and occupational therapists, athletic coaches, nurses, and fitness trainers 6. Their mobility makes them important to quality of life

movement of synovial joints *

- There is a vocabulary for joint movements used in many medical and scientific fields 1. Many terms presented in pairs with opposite or contrasting meanings 2. Need to understand anatomical planes and directional terms 3 Zero positions: the position of a joint when a person is in the standard anatomical position - Joints movements described as deviating from the zero position or returning to it

mechanical advantage (MA)

- Two kinds of advantage conferred by a lever: (Exerting more force against a resisting object than the force applied to the lever) 1. Moving a heavy object with help of crowbar: - Moving the resisting object farther or faster than the effort arm is moved 2. Movement of rowing a boat: - A single lever cannot confer both advantages As one increases, the other decreases - Mechanical advantage (MA) of a level- the ratio of its output force to its input force

exercise and articular cartilage

-Exercise warms synovial fluid *Becomes less viscous, more easily absorbed by cartilage -Cartilage then swells and provides a more effective cushion *Warm-up period before vigorous exercise helps protect cartilage from undue wear and tear -Repetitive compression of nonvascular cartilage during exercise squeezes fluid and metabolic waste out of the cartilage -When weight removed, cartilage absorbs synovial fluid like a sponge taking in oxygen and nutrients to the chondrocytes -Without exercise, cartilage deteriorates more rapidly from inadequate nutrition and waste removal

abduction and adduction

1. Abduction: movement of a body part in the frontal plane away from the midline of the body - Hyperabduction: raise arm over back or front of head 2. Adduction: movement in the frontal plane back toward the midline - Hyperadduction: crossing fingers, crossing ankles

ball- and-socket and condylar (ellipsoid) joints *

1. Ball-and-socket joints: - Smooth, hemispherical heads fits within cup-like socket - Only multiaxial joints in body - Examples: shoulder and hip 2. Condylar (ellipsoid) joints: - Oval convex surface of one bone fits into a complementary- shaped depression on the other - Biaxial joints- movement in two places -Examples: radiocarpal joints, metacarpophalangeal joints

circumduction

1. Circumduction: one end of an appendage remains stationary while other end makes a circular motion - Example: an artist circumducts upper limb when painting a circle on a canvas

dorsiflexion, plantar flexion, inversion, eversion

1. Dorsiflexion: elevating toes as you do while swinging foot forward to take a step (heel strike) 2. Plantar flexion: extending foot so that toes point downward as in standing on tiptoe (toe-off) 3. Inversion: movement in which the soles are turned medially 4. Eversion: movement in which the soles are turned laterally

elevation and depression

1. Elevation: movement that raises a body part vertically in the frontal plane 2. Depression: movement that lowers a body part in the same plane

flexion and extension of head and trunk

1. Flexion: forward bending movements at the waist or neck 2. Extension: straightens trunk or neck 3. Hyperextension: bending over backward 4. Lateral flexion: tilting the head or trunk to the right or left at the midline

flexion and extension at elbow and wrist

1. Flexion: movement that decreases joint angle - Common in hinge joint 2. Extension: movement that straightens a joint and returns a body part to the zero position 3. Hyperextension: extension of a joint beyond the zero position - Flexion and extension occur at nearly all diarthroses, hyperextension is limited to a few

hinge joints and pivot joints *

1. Hinge joint: - One bone with convex surface fits into a concave depression of another bone - Monoaxial joints: move freely in one place - Examples: elbow, knee, joins within fingers, toes 2. Pivot joints: - A bone spins on its longitudinal axis - Monoaxial joints - Examples: atlantoaxial joint (C1 and C2), radioulnar joint at the elbow

excursion: side-to-side grinding during chewing

1. Lateral excursion: right or left movement from the zero position 2. Medial excursion: movement back to the median, zero position

two ligaments support joint

1. Lateral ligament—prevents posterior displacement of mandible 2. Sphenomandibular ligament—on the medial side - Deep yawn or strenuous depression can dislocate the TMJ • Condyles pop out of fossa and slip forward• Relocated by pressing down on molar teeth while pushing the jaw backward

special movements of hand and digits 2

1. Palmar abduction: moving thumb away from hand and pointing it anteriorly 2. Radial abduction: moving thumb away from the index finger (90 degrees) 3. Flexion of thumb: tip of thumb directed toward palm 4. Extension of thumb: straightening the thumb 5. Opposition: moving thumb to touch tip of a finger 6. Reposition: returning thumb to the zero position

protraction and retraction

1. Protraction: the anterior movement of a body part in the transverse (horizontal) plane 2. Retraction: posterior movement

special movements of hand and digits

1. Radial flexion: tilting hand toward thumb 2. Ulnar flexion: tilting hand toward little finger 3. Abduction vs. Adduction of the fingers: spreading them apart vs. bringing them together 4. Flexion vs. extension of fingers: curling vs. straighten them

rotation

1. Rotation: movement in which a bone spins on its longitudinal axis - Rotation of trunk, thigh, head, or arm - Medial (internal) rotations turns the bone inward - Lateral (external) rotations turns the bone outward

special movements of the foot

1. Supination of foot: complex combination of plantar flexion, inversion, and adduction 2. Pronation of foot: complex combination of dorsiflexion, eversion, and abduction

the knee joint locking

Ability to lock and unlock knees: - Important aspect of human bipedalism - When knee fully extended, ACL allows locking • Femur rotates medially on the tibia, major knee ligaments taut - To unlock knee, popliteus contracts and rotates femur laterally • Lateral rotation of femur untwists ligaments

ligaments supporting hip joint *

Acetabular labrum—horseshoe-shaped ring of fibrocartilage that deepens socket: - Dislocations are rare • Ligaments supporting hip joint- Iliofemoral and pubofemoral — anterior- Ischiofemoral ligament —posterior- When standing, ligaments become twisted and pull head of femur tightly into acetabulum - Transverse acetabular ligament bridges gap on inferior margin ofacetabular labrum • Round ligament (ligamentum teres) —arises from fovea capitis and attaches to lower margin of acetabulum - Contains artery that supplies blood to head of femur

ankle ligaments

Anterior and posterior tibiofibular ligaments: bind tibia to fibula - Multipart medial (deltoid) ligament: binds tibia to the foot on the medial side - Multipart lateral (collateral) ligament: binds fibula to the foot on the lateral side - Calcaneal (Achilles) tendon: extends from the calf muscles to the calcaneus • Plantarflexes the foot and limits dorsiflexion - Sprains (torn ligaments and tendons) are common at the ankle• Pain and immediate swelling

arthritis

Arthritis—a broad term for pain and inflammation of joints • Most common crippling disease in the United States • Rheumatologists—physicians who treat arthritis and other joint disorders • Osteoarthritis (OA)—most common form of arthritis - "Wear-and-tear arthritis" - Results from years of joint wear - Articular cartilage softens and degenerates - Accompanied by crackling sounds called crepitus - Bone spurs develop on exposed bone tissue causing pain

the six classes of synovial joints *

Ball-and-socket, condylar, saddle, plane, hinge, pivot

the elbow joint *

Elbow—a hinge that includes two articulations: - Humeroulnar joint: trochlea of the humerus joins trochlear notch of the ulna - Humeroradial joint: capitulum of humerus meets head of radius - Both articulations enclosed in one joint capsule - Olecranon bursa on posterior side of elbow eases movements of tendons - Radial (lateral) collateral ligament and ulnar (medial)collateral ligaments restrict side-to-side motions

glenohumeral (humeroscapular) joint *

Glenohumeral (humeroscapular) joint—hemispherical head of humerus articulates with glenoid cavity of scapula - Most freely mobile joint in body - Shallow glenoid cavity and loose shoulder joint capsule sacrifice stability for freedom of movement - Glenoid labrum: fibrocartilage ring that deepens glenoidcavity • Shoulder supported by biceps brachii tendon anteriorly and also rotator cuff tendons - Tendons fuse to joint capsule and strengthen it - Supraspinatus, infraspinatus, teres minor, and subscapularis

knee injuries and arthroscopic surgery

Highly vulnerable to rotational and horizontal stress Most common injuries are to the menisci and anterior cruciate ligament (ACL) Heal slowly due to scanty blood flow

knee injuries and arthroscopic surgery 1

Highly vulnerable to rotational and horizontal stress • Most common injuries are to the menisci and anterior cruciate ligament (ACL) • Heal slowly due to scanty blood flow

the knee joint capsule

Joint capsule encloses only the lateral and posterior aspects of the knee: - Anterior aspect covered by patellar ligament and lateral and medial retinacula • All are extensions of the tendon of quadriceps femoris muscle • Knee stabilized by:- Quadriceps tendon in front - Tendon of semimembranosus muscle on rear of thigh - Lateral meniscus and medial meniscus —C-shaped cartilages within joint capsule • Absorb shock and prevent side-to-side rocking• Joined by transverse ligament

the knee joint: ACL and PCL *

Popliteal (posterior) region- Extracapsular ligaments• Fibular (lateral) collateral ligament • Tibial (medial) collateral ligament- Intracapsular ligaments cross each other to form X • Anterior cruciate ligament (ACL)- Prevents hyperextension of knee when ACL is pulled tight - Common site of knee injury • Posterior cruciate ligament (PCL)- Prevents femur from sliding off tibia

rheumatoid arthritis

Rheumatoid arthritis (RA)—autoimmune attack against the joint tissues - Misguided antibodies (rheumatoid factor) attack synovial membrane, enzymes in synovial fluid degrade the articular cartilage, joint begins to ossify - Ankylosis: solidly fused, immobilized joint - Remissions occur, steroids and aspirin control inflammation • Arthroplasty—replacement of diseased joint with artificial device called prosthesis

temporomandibular (jaw) joint (TMJ) *

Temporomandibular (jaw) joint (TMJ)—articulation of the condyle of the mandible with the mandibular fossa of the temporal bone - Combines elements of condylar, hinge, and plane joints - Synovial cavity of the TMJ is divided into superior and inferior chambers by an articular disc

TMJ structure *

Temporomandibular joint (TMJ) syndrome - May affect as many as 75 million Americans • Signs and symptoms: - Clicking sounds in the jaw, imitation of jaw movement - Pain radiating from jaw down the neck, shoulders, and back - Can cause moderate intermittent facial pain, or severe headaches, vertigo (dizziness), tinnitus (ringing in the ears) • Cause of syndrome: - Caused by combination of psychological tension and malocclusion (misalignment of teeth) • Treatment: - Psychological management, physical therapy, analgesic and anti- inflammatory drugs, corrective dental appliances to align teeth properly

five principal ligaments support shoulder

Three are called the glenohumeral ligaments: - Coracohumeral ligament - Transverse humeral ligament • Four bursa occur at the shoulder - Subdeltoid, subacromial, subcoracoid, and subscapularbursae

the knee joint

Tibiofemoral (knee) joint—largest and most complex diarthrosis of the body • Primarily a hinge joint - Capable of slight rotation and lateral gliding when knee is flexed - Patellofemoral joint—gliding joint

shoulder dislocation *

Very painful and sometimes causes permanent damage • Downward displacement of the humerus is the most common shoulder dislocation - Rotator cuff protects the joint in all directions but inferiorly - Joint protected from above by coracoid process, acromion,and clavicle - Dislocations most often occur when the arm is abductedand then receives a blow from above • Children especially prone to dislocation

talocrural joint

• Talocrural (ankle) joint—includes two articulations: - Medial joint: between tibia and talus - Lateral joint: between fibula and talus • Both articulations enclosed by one joint capsule • Malleoli of tibia and fibula overhang the talus on either side and prevent side-to-side motion • More restricted range of motion than the wrist