Joints Function: hold bones together & Increase mobility

Classification of Joints Structural classification -binding material & presence or absence of a joint cavity Fibrous Cartilagenous Synovial Functional classification - amount of movement Synarthroses (immovable joints) Amphiarthroses (slightly movable joints) Diarthroses (freely movable joints)

Fibrous joints/Synarthroses Bones connected by dense regular connective tissue No joint cavity Slightly immovable or not at all Types Sutures Between tibia/fibula

Cartilagenous joints/ Amphiarthoroses Articulating bones united by cartilage Lack a joint cavity Not highly movable Ex Intervertebral discs Pubic symphysis of the pelvis

Amphiarthroses Also pubic symphsis

Synovial joints/ Diarthroses Include most of the body’s joints freely movable All contain fluid-filled joint cavity

General Structure of Synovial Joints Articular cartilage Spongy cushions absorb compression Protects ends of bones from being crushed Synovial cavity Potential space Small amount of synovial fluid 3. Articular capsule layered covering of joint

General structure of synovial joints (cont.) 4. Synovial fluid Nourishes cartilage and functions as slippery lubricant 5. Reinforcing ligaments (some joints) link bones 6. Nerves Detect pain Monitor stretch 7. Blood vessels

General structure of synovial joints

Joint stability Articular surfaces Ligaments Muscle tone Shape usually plays only minor role Some deep sockets or grooves do provide stability Ligaments Usually the more, the stronger the joint Can stretch only 6% beyond normal length before tear Once stretched, stay stretched Muscle tone Constant, low level of contractile force Keeps tension on the ligaments Especially important at shoulders, knees, arches of foot

Movements allowed by synovial joints Gliding Angular movements: hor i the angle between two bones DO TOGETHER Flexion Extension Abduction Adduction Circumduction Rotation Special movements

Special movements Pronation Protraction Supination Retraction Dorsiflexion Plantar flexion Inversion Eversion Protraction Retraction Elevation Depression Opposition

Joint movements pics (from Marieb, 4th ed.)

Synovial joints classified by shape (of their articular surfaces) Plane (see right) Hinge (see right) Pivot Condyloid Saddle Ball-and-socket

Shoulder (glenohumeral) joint Selected synovial joints Shoulder (glenohumeral) joint Stability sacrificed for mobility Ball and socket: head of humerus with glenoid cavity of scapula Glenoid labrum: rim of fibrocartilage Thin, loose capsule Strongest ligament: coracohumeral Muscle tendons help stability Disorders Rotator cuff muscles add to stability Biceps tendon is intra-articular

Elbow joint Hinge: allows only flexion and extension Annular ligament of radius attaches to capsule Capsule thickens into: Radial collateral ligament Ulnar collateral ligament Muscles cross joint Trauma

Wrist joint Two major joint surfaces Several ligaments stabilize Radiocarpal joint Between radius and proximal carpals (scaphoid and lunate) Condyloid joint Flexion extension adduction, abduction, circumduction Intercarpal or midcarpal joint Between the proximal and distal rows of carpals

Hip (coxal) joint Ball and socket Moves in all axes but limited by ligaments and deep socket Three ext. ligaments “screw in” head of femur when standing Iliofemoral Pubofemoral Ischiofemoral

Acetabular labrum diameter smaller than head of femur Dislocations rare Ligament of head of femur supplies artery Muscle tendons cross joint Hip fractures common in elderly because of osteoporosis

Right hip, AP view

Knee joint Largest and most complex joint Primarily a hinge Compound and bicondyloid: femur and tibia both have 2 condyles Femoropatellar joint shares joint cavity At least a dozen bursae Prepatellar Suprapatellar

Lateral and medial menisci “torn cartilage” Capsule absent anteriorly Capsular and extracapsular ligaments Taut when knee extended to prevent hyperextension

Fibular and tibial collateral ligaments Patellar ligament Continuation of quad tendon Medial and lateral retinacula Fibular and tibial collateral ligaments Called medial and lateral Extracapsular Oblique popliteal Arcuate popliteal

Cruciate ligaments Cross each other (cruciate means cross) Anterior cruciate (ACL) Anterior intercondylar area of tibia to medial side of lateral condyl of femur Posterior cruciate Posterior intercondylar area of tibia to lateral side of medial condyl Restraining straps Lock the knee

Cruciate ligaments

Knee injuries Flat tibial surface predisposes to horizontal injuries Lateral blow: multiple tears ACL injuries Stop and twist Commoner in women athletes Heal poorly Require surgery

Ankle joint Hinge joint Distal tibia and fibula to talus Dorsiflexion and plantar flexion only Medial deltoid ligament Lateral ligaments: 3 bands Anterior talofibular Posterior talofibular Calcaneofibular Anterior and posterior tibiofibular (syndesmosis)

Right ankle, lateral view

Temporomandibular joint (TMJ) Head of mandible articulates with temporal bone Disc protects thin mandibular fossa of temporal bone Many movements Demonstrate movements together Disorders common

Table of Joint Types Functional across Structural down Synarthroses (immovable joints) Amphiarthroses (some movement) Diarthroses (freely movable) Bony Fusion Synostosis (frontal=metopic suture; epiphyseal lines) Fibrous Suture (skull only) -fibrous tissue is continuous with periosteum Gomphoses (teeth) -ligament is periodontal ligament Syndesmoses -ligaments only between bones; here, short so some but not a lot of movement (example: tib-fib ligament) -ligament longer (example: radioulnar interosseous membrane) Cartilagenous (bone united by cartilage only) Synchondroses -hyaline cartilage (examples: manubrium-C1, epiphyseal plates) Sympheses -fibrocartilage (examples: between discs, pubic symphesis Synovial Are all diarthrotic

Sternoclavicular joint Saddle joint Only other example is trapezium and metacarpal 1 (thumb), allowing opposion Sternum and 1st costal (rib) cartilage articulate with clavicle Very stable: clavicle usually breaks before dislocation of joint Only bony attachment of axial skeleton to pectoral girdle Demonstrate movements together

Disorders of joints Injuries Inflammatory and degenerative conditions Sprains Dislocatios Torn cartilage Inflammatory and degenerative conditions Bursitis Tendinitis Arthritis Osteoarthritis (“DJD” – degenerative joint disease) Rheumatoid arthritis (one of many “autoimmune” arthritites) Gout (crystal arthropathy)