Joints Classification of Joints Functional classification Focuses on

Joints

Classification of Joints § Functional classification (Focuses on amount of movement) § Synarthroses (immovable joints) § Amphiarthroses (slightly movable joints) § Diarthroses (freely movable joints) § Structural classification (Based on the material binding them and presence or absence of a joint cavity) § Bony fusion § Fibrous § Cartilagenous § Synovial

Table of Joint Types Functional across Synarthroses (immovable joints) Amphiarthroses (some movement) Diarthroses (freely movable) Syndesmoses -ligament longer (example: radioulnar interosseous membrane) Structural down Bony Fusion Synostosis (frontal suture; epiphyseal lines) Fibrous Suture (skull only) -fibrous tissue is continuous with periosteum Syndesmoses -ligaments only between bones; here, short so some but not a lot of movement (example: tib-fib ligament) Cartilagenous (bone united by cartilage only) Synchondroses -hyaline cartilage (examples: manubrium-C 1, epiphyseal plates) Sympheses -fibrocartilage (examples: between discs, pubic symphesis Synovial Are all diarthrotic

Fibrous joints § Bones connected by fibrous tissue: dense regular connective tissue § No joint cavity § Slightly immovable or not at all § Types § Sutures § Syndesmoses

Sutures § Only between bones of skull § Fibrous tissue continuous with periosteum § Ossify and fuse in middle age: now technically called “synostoses”= bony junctions

Syndesmoses § In Greek: “ligament” § Bones connected by ligaments only § Amount of movement depends on length of the fibers: longer than in sutures

Gomphoses § Is a “peg-in-socket” § Only example is tooth with its socket § Ligament is a short periodontal ligament

Cartilagenous joints § § Articulating bones united by cartilage Lack a joint cavity Not highly movable Two types § Synchondroses (singular: synchondrosis) § Sympheses (singular: symphesis)

Synchondroses § § Literally: “junction of cartilage” Hyaline cartilage unites the bones Immovable (synarthroses) Examples: § Epiphyseal plates § Joint between first rib’s costal cartilage and manubrium of the sternum

Sympheses § Literally “growing together” § Fibrocartilage unites the bones § Slightly movable (amphiarthroses) § Resilient shock absorber § Provide strength and flexibility § Hyaline cartilage on articular surfaces of bones to reduce friction § Examples § Intervertebral discs § Pubic symphysis of the pelvis

Synchondroses and sympheses Also pubic symphsis

Synovial joints § Include most of the body’s joints § All are diarthroses (freely movable) § All contain fluid-filled joint cavity

General Structure of Synovial Joints 1. Articular cartilage § § § Hyaline Spongy cushions absorb compression Protects ends of bones from being crushed 2. Joint (synovial) cavity § § Potential space Small amount of synovial fluid

General structure of synovial joints (cont. ) 3. Articular (or joint) capsule § Two layered § Outer*: fibrous capsule of dense irregular connective tissue continuous with periosteum § § Inner*: synovial membrane of loose connective tissue (makes synovial fluid) Lines all internal joint surfaces not covered by cartilage* *

General structure of synovial joints (cont. ) 4. Synovial fluid § § § Filtrate of blood Contains special glycoproteins Nourishes cartilage and functions as slippery lubricant 5. Reinforcing ligaments (some joints) § § § Capsular (most) – thickened parts of capsule Extracapsular Intracapsular

General structure of synovial joints (cont. ) 6. Nerves § Detect pain § Monitor stretch (one of the ways of sensing posture and body movements) 7. Blood vessels § Rich blood supply § Extensive capillary beds in synovial membrane (produce the blood filtrate)

General structure of synovial joints

Some joints… § Articular disc or meniscus (literally “crescent”) § Only some joints § Those with bone ends of different shapes or fitting poorly § Some to allow two kinds of movement (e. g. jaw) § Of fibrocartilage § Examples: knee TMJ (temporomandibular joint) sternoclavicular joint

Bursae and tendon sheaths § § Contain synovial fluid Not joints but often associated with them Act like ball bearings Bursa means “purse” in Latin § Flattened sac lined by synovial membrane § Where ligaments, muscles, tendons, or bones overlie each other and rub together § Tendon sheath § Only on tendons subjected to friction

Bursae and tendon sheaths

Joint stability § Articular surfaces § 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 Supination Dorsiflexion Plantar flexion Inversion Eversion § § § Protraction Retraction Elevation Depression Opposition

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

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

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 1. Radiocarpal joint § Between radius and proximal carpals (scaphoid and lunate) § Condyloid joint § Flexion extension adduction, abduction, circumduction 2. 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

§ 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

Sternoclavicular joint § Saddle joint § Only other example is trapezium and metacarpal 1 (thumb), allowing opposion § Sternum and 1 st 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 § 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)

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