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Joints

Joints. Classification of Joints. Functional classification (Focuses on amount of movement) Synarthroses (immovable joints) Amphiarthroses (slightly movable joints) Diarthroses (freely movable joints) Structural classification

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Joints

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  1. Joints

  2. 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

  3. Table of Joint Types

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

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

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

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

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

  9. 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

  10. 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

  11. Synchondroses and sympheses Also pubic symphsis

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

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

  14. 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* * * *

  15. 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

  16. 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)

  17. General structure of synovial joints

  18. 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

  19. 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

  20. Bursae and tendon sheaths

  21. 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

  22. 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

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

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

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

  26. 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

  27. 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

  28. Wrist jointTwo major joint surfacesSeveral 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

  29. 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

  30. 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

  31. Right hip, AP view

  32. 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

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

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

  35. 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

  36. Cruciate ligaments

  37. 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

  38. 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)

  39. Right ankle, lateral view

  40. 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

  41. 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

  42. 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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