CLASSIFICATION

Mobility

1. Synarthrosis – immovable

2. Amphiarthrosis – slightly movable

3. Diarthrosis – freely movable

Structural classification

1. Fibrous joints – some, slightly movable, synarthrotic

-a. Sutures – connective tissue fibers penetrate articulating bones; only in skull

-b. Syndesmosis – cord or sheet connective tissue; movement vary

-c. Gomphosis – peg in socket joint fibrous joint; tooth and alveolar socket

2. Cartilaginous joints – articulating bones are joined by cartilage

-a. Synchondrosis – a bar or plate of hyaline cartilage; bone growth epiphyseal plate

-b. Symphysis – pad or disc of fibrocartilage between; intervertebral disc; pubic

3. Synovial joints – most joints; articulating bones separated by fluid filled cavity

SYNOVIAL JOINTS

General structure

1. Articular cartilage – hyaline cartilage on opposing bone surfaces; spongy cushions

2. Joint (synovial cavity) – formed by the articular capsule; contains synovial fluid

3. Articular capsule – a double layered capsule that encloses the synovial cavity

-a. Fibrous capsule – external layer; tough, flexible; continuous with the periosteum

-b. Synovial membrane – inner layer; loose connective tissue; covers except hyaline

4. Synovial fluid – in synovial cavity; blood filtrate from capillaries synovial membrane

5. Reinforcing ligaments – reinforce and strengthen the synovial joint

-a. Intrinsic (capsular) ligaments – thickened sections of the fibrous capsule

-b. Extracapsular ligaments – found outside capsule

-c. Intracapsular ligaments – covered with synovial membrane so not in joint cavity

6. Fatty pads – between fibrous capsule and synovial membrane in some; extra cushioning

7. Minisci (articular disc) – wedges of fibrocartilage from joint capsule; improve fit

8. Bursae – flat sacs with synovial fluid secreted by synovial membrane; less friction

9. Tendon sheaths – elongated bursae that wraps around a tendon

Factors influencing stability

1. Articular surfaces – may contribute little to stability, surfaces not complementary

2. Ligaments – usually the more ligaments the more stable the joint

3. Muscle tone – muscle tendon crossing the joint is the most important stabilizing factor

Range of motion

1. Nonaxial movement – slipping movements only; no axis of movement

2. Uniaxial movement – movement in one plane

3. Biaxial movement – movement in two planes

4. Multiaxial movement – movement in or around all three planes

Types of movement

1. Gliding movements – flat surfaces slipping over same; carpals, tarsals, and vertebrae

2. Angular movements – can occur in any of the body planes

-a. Flexion – decrease angle of joint; sagittal; distance between origin and insertion

-b. Extension – increase angle of joint; sagittal; increases distance between them

-c. Dorsiflexion – movement of the foot; superior surface approaches the leg

-d. Plantar flexion – movement of the foot; superior surface moves away from the leg

-e. Abduction – movement away from midline of body or spreading fingers or toes

-f. Adduction – opposite abduction; movement toward midline of the body, hand or foot

-g. Circumduction – movement of limb to form a cone; joint as apex; distal end as base

3. Rotation – movement along its own long axis; head, shoulder, and hip; lateral or medial

4. Special movements – do not fit any previous categories

-a. Supination – movement palm anteriorly or superiorly; anatomical position

-b. Pronation – movement palm posteriorly or inferiorly; radius and ulna are crossed

-c. Inversion – movement of the sole medially; frontal plane

-d. Eversion – movement of the sole laterally; frontal plane

-e. Protraction – anterior movement; jutting out ones jaw; transverse plane

-f. Retraction – posterior movement; pulling jaw back; transverse plane

-g. Elevation – movement of body part superiorly; closing the jaw

-h. Depression – movement of body part inferiorly; opening your mouth

-i. Opposition – tip of the thumb can touch the tip of other fingers

Types of synovial joints

1. Plane joints – allows nonaxial gliding movements; carpals and tarsals

2. Hinge joints – cylindrical projection into trough; uniaxial; elbow and finger joints

3. Pivot joints – projection fits in ring; uniaxial rotation; atlas, dens of axis; radioulnar

4. Condyloid joints – elliptical projection and depression; biaxial; knee, jaw, wrist

5. Saddle joints – both convex and concave surface; biaxial; carpometacarpal, thumb

6. Ball-and-socket joints – spherical projection into cup socket; multiaxial; shoulder, hip

SELECTED SYNOVIAL JOINTS

Shoulder (glenohumeral) joint

1. Articulating surfaces – glenoid cavity of scapula; dome head of the humerus; mobility

2. Joint type – ball and socket joint

3. Articular capsule – from margin glenoid cavity to the anatomical neck of the humerus

4. Ligaments – not the major stabilizers

-a. Coracohumeral ligament – from coracoid process to greater tubercule of the humerus

-b. Glenohumeral ligaments – three weak, missing ligaments; strengthen anterior part

-c. Transverse humeral ligament – between the humeral tubercles; attached to tendon

5. Joint stabilization – muscle tendons which cross joint cavity; rotator cuff easily injured

6. Movements – great deal of movement; multiaxial movement

Hip (coxal) joint

1. Articulating surfaces – spherical head of femur and deep acetabulum of coxal bone

2. Joint type – ball in socket joint

3. Articular capsule – from rim of the acetabulum to neck of the femur

4. Ligaments – very strong

-a. Ileofemoral ligament – anterior V shaped; from the anterior iliac spine

-b. Pubofemoral ligament – also anterior; from the pubic bone

-c. Ischiofemoral ligament – spiraling posterior ligament

-d. Ligamentum teres – femur head lower lip of the acetabulum; little stabilizer, arterial

5. Joint stability – socket of articulating surfaces and strong ligaments; muscles help

6. Movements – a multiaxial joint; less freedom than shoulder

Elbow joint

1. Articulating surfaces – couple to be considered

-a. Elbow – trochlea of the ulna and trochlear notch of the humerus

-b. Proximal radioulnar – between head of radius and ulna

2. Joint types – most important is that of the elbow

-a. Elbow – a uniaxial hinge joint; only flexion and extension are possible

-b. Proximal radioulnar – uniaxial pivot joint

3. Articular capsule – extends from humerus to ulna and to annular ligament of the radius

4. Ligaments – collaterals restrict movement

-a. Annular ligament – around head of radius; not really for stabilization of elbow joint

-b. Ulnar (medial) collateral ligament – medial reinforcement of capsule

-c. Radial (lateral) collateral ligament – lateral reinforcement of capsule

5. Stabilizers – all the ligaments mentioned plus muscle tendons which cross the elbow

6. Movements – restricted by ligaments

-a. Elbow – flexion and extension only; muscles, tendons, olecranon process, fossa

-b. Proximal radioulnar – pivot joint; uniaxial rotation of radius; pronation and supination

Knee joint

1. Articulating surfaces – is actually three joints in one

-a. Femoropatellar joint – between the patella and the patellar surface of the femur

-b. Tibiofemoral joint – two joints; lateral and medial

2. Meniscus – C shaped pads of fibrocartilage; help deepen articulating surfaces

3. Joint type – condyloid joint

4. Articular capsule – sides and posterior; covers femoral and tibial condyles

5. Patellar ligaments – three; are actually extensions of thigh muscles

6. Extracapsular ligaments – found outside of capsule

-a. Fibular (lateral) collateral ligament – lateral epicondyle of femur to head of the fibula

-b. Tibial (medial) collateral ligament – from medial epicondyle of femur to tibial shaft

-c. Popliteal ligaments – reinforce the joint posteriorly

7. Intracapsular ligaments – cross each other as they pass through the joint capsule

-a. Interior crucinate ligament – anterior intercondylar of tibia to lateral condyle of femur

-b. Posterior crucinate ligament – posterior intercondylar of tibia to medial condyle, femur

8. Joint stability – relies on the tendons of thigh muscles

9. Tibial movement – several

-a. Extension – as occurs when standing is complex

-b. Rotation – medial and lateral rotation when flexed

10. Sports injuries – highly susceptible; tibial collateral ligament, tears medial meniscus

HOMEOSTATIC IMBALANCES

Joint injuries

1. Sprains – ligaments are stretched or torn; heal slowly because of poor vascularization

2. Cartilage injuries – common menisci of the knee; growth plate; surgical removal

3. Dislocations (luxation) – bones forced out of their normal position; reduced; repeated

Inflammatory and degenerative conditions

1. Bursitis – mechanical or infectious factors; anti-inflammatory drugs, aspiration of fluid

2. Tendonitis – inflammation of tendon sheaths very similar to bursitis

3. Osteoarthritis – most common form; aging; enzyme breaks down articular cartilage

-a. Bony spurs – roughen ends; restrict movement

4. Rheumatoid arthritis – autoimmune disease in which the immune system attacks the

-a. Inflammatory cells – invade the joint cavity; articular cartilage breaks down bones of

-b. Ankylosis – joint are fused together by scar tissue which latter ossifies; deformities

5. Gouty arthritis – uric acid in blood; crystallization in joint cavities

-a. Untreated – can be destructive as bone ends fuse and immobilize the joint

-b. Treatment – good drug treatments, dietary, and life style changes; genetic component