Articulations The place of union or junction between two or more bones of the skeleton (also between cartilage and bones/teeth and bones - allow for movement - structure of joint determines the range of movement - the closer the fit, the stronger the joint; the looser the fit, the more movement ARTHROLOGY – The science concerned with the study of joints, includes function, structure, classification and any dysfunctions KINESIOLOGY – the science concerned with the functional relationship, or biomechanics, of the skeleton, joints and muscles as they work together to produce coordinated movement.

I.Classification of joints A.Structural classification – based on the presence or absence of a joint cavity and the kind of supportive tissue surrounding the joint. Three types: 1. Fibrous joints – lack a joint cavity; fibrous connective tissue connects articulating joints 2. Cartilaginous joints – lacks a joint cavity; cartilage binds articulating bones 3. Synovial joints – has a joint cavity; ligaments help support articulating bones

B. Functional classification – based on the degree of movement permitted within the joint Three types: 1.Synarthrosis – immoveable joints 2.Amphiarthrosis – slightly moveable joints 3.Diarthrosis – freely moveable joints

II. Breakdown by functional classification A.Synarthroses (immoveable joints) 1.Suture – strongest joint by structure - fibrous joints found between flat bones of the skull - irregular structure that gives strength and reduces fractures 2.Gomphoses - fibrous joints that occur between teeth and the supporting bones of the jaw. - located where the root of a tooth is attached to the periodontal ligament of the alveolus (socket) of the bone.

3. Synchondroses - cartilaginous joint with hyaline cartilage as the connective tissue - some are temporary and form the epiphyseal growth plates between the diaphysis and epiphysis in the long bones of children

B. Amphiarthroses – slightly moveable joint 1.Syndesmoses -Fibrous joint found only in the forearm and leg where adjacent bones are held together by collagenous fibers -Characteristic of the side-to-side joints between tibia-fibula and the radius-ulna (allows rotation) 2. Symphyses (symphysis pubis, and intervertebral discs) -Cartilaginous joint separated by a pad of fibrocartilage; allows for limited movement -Only limited motion is possible at each joint, the combined movement allows for extensive movement (vertebrae)

C. Diarthroses – freely moveable 1.Characteristics: a. provides a wide range of precise, smooth movements while maintaining stability, strength, and some rigidity in the body b. most complex and varied of the three major types c. range of movement is limited by three factors: - structure of the bones participating in the articulation - the strength and tautness of the associated ligaments, tendons and joint capsule - the size, arrangement and action of the muscles that span the joint (“double jointed” is a misnomer; not two joints, but extreme maneuverability due possibly to loose ligaments and tendons)

2. Structure of the synovial joint a. Synovial Cavity – space between the articulating bones refers to the structural classification b. Articular Cartilage – present in all diarthrotic joints (2 mm thick), hyaline cartilage covers the articulating surface c. Articular Capsule – surrounds the entire diarthrotic joint (two layers): FIBROUS LAYER – outer layer - dense, irregular connective tissue - attaches to periosteum of bones - permits movement and resists dislocation - fibers from ligaments; hold bones together

SYNOVIAL MEMBRANE – Inner layer - secretes synovial fluid (looks,feels like uncooked egg white) - lubricates joints and nourishes cartilage - houses phagocytic cells that remove microbes and debris

d. Accessory ligaments – some outside of articular capsule, some within e. Articular discs – pads of fibrocartilage called menisci (meniscus = singular) -Stabilize joint by forming tighter fit -Tearing of these is called torn cartilage f. Bursae – sac-like structures between moving parts (help cushion and reduce friction -Filled with synovial fluid -Found between skin and bone, tendon and bone, muscle and bone, ligaments and bone

3. Types of synovial joints a.Gliding joint – simplest type - Allow only side-to-side and back-and-forth movements with minimal rotation -Surfaces are usually flat or slightly concave/convex -EX: Intercarpal/intertarsal, sternoclavicular, between adjacent vertebrae b. Saddle joint- looks like a saddle -Each articular process has a concave surface in one direction, convex in the other -Is a modified condyloid joint allowing a wider range of movement -EX: only associated with the thumb (located at the articulation of the trapezium of the carpus with the first metacarpal bone)

c. Hinge joint – permits bending in only one direction (similar to the hinge of a door) -One surface is always concave and the other is convex -Most common type of synovial joint -EX: knee, humeroulnar, phalanges

d. Pivot – movement is limited to rotation about a central axis -One surface is rounded and fits into a depression of another -EX: proximal articulation of the radius and ulna, articulation between atlas and axis e. Ball-and socket – formed by articulation of a rounded convex surface with a cuplike cavity -Provides the greatest range of movement of all joints -EX: hip and shoulder joints f. Condyloid or ellipsoid – structured so that an oval, convex surface of one bone fits into an elliptical, concave depression of another bone - Allows for angular movement in two directions (up and down and side- to-side motion) - EX: radiocarpal joint

III. Problems A.Clinical considerations 1. Hyperextension 2. Strained joint 3. Sprain 4. Luxation 5. Bursitis 6. Tendonitis B. Diseases of joints Arthritis - Arthritis - 1. Rheumatoid arthritis 1. Rheumatoid arthritis 2. Osteoarthritis 2. Osteoarthritis 3. Gouty arthritis 3. Gouty arthritis

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