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) . Fibrous mostly synarthroses . Cartilagenous mostly amphiarthroses . Synovial diarthroses Table of Joint Types Functional across Synarthroses Amphiarthroses Diarthroses (immovable joints) (some movement) (freely movable) Structural down Bony Fusion Synostosis (frontal=metopic suture; epiphyseal lines) Fibrous Suture (skull only) Syndesmoses Syndesmoses -fibrous tissue is -ligaments only -ligament longer continuous with between bones; here, (example: radioulnar periosteum short so some but not interosseous a lot of movement membrane) (example: tib-fib Gomphoses (teeth) ligament) -ligament is periodontal ligament Cartilagenous Synchondroses Sympheses (bone united by -hyaline cartilage -fibrocartilage cartilage only) (examples: (examples: between manubrium-C1, discs, pubic epiphyseal plates) 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 . Gomphoses 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 . “Weeping” lubricatioin 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 . Protraction . Supination . Retraction . Dorsiflexion . Elevation . Plantar flexion . Depression . Inversion . Opposition . Eversion 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 Selected synovial joints Shoulder (glenohumeral) joint . Stability sacrificed for mobility . Ball and socket: head of humerus with glenoid cavity of scapula Rotator cuff muscles add to stability . Glenoid labrum: rim of fibrocartilage . Thin, loose capsule . Strongest ligament: coracohumeral . Muscle tendons help stability . Disorders 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 1. Radiocarpal joint . Between radius and Two major joint surfaces proximal carpals Several ligaments stabilize (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 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 . 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) .