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DictionarySeejointAC joint
AC Joint The joint between the acromium process of scapula and the distal end of the clavicle; it is the location of most shoulder separations, which are particularly common in collision sports—e.g., ice hockey, rugby, American football, and Australian rules football.AC joint Acromio-clavicular joint Orthopedics The point where the acromium process of scapula and the distal end of the clavicle meet, which is the location of most frequent shoulder separations.joint (joynt) [Fr. jointe, fr L. junctio, a joining] TYPES OF JOINTSTYPES OF JOINTSTYPES OF JOINTSTYPES OF JOINTSTYPES OF JOINTSTYPES OF JOINTSThe place where two or more bones meet. Some joints are fixed or immobile attachments of bones; other joints allow the bones to move along each other. A joint usually has a thin, smooth articular cartilage on each bony surface and is enclosed by a joint capsule of fibrous connective tissue. A joint is classified as immovable (synarthrodial), slightly movable (amphiarthrodial), or freely movable (diarthrodial). A synarthrodial joint is one in which the two bones are separated only by an intervening membrane, such as the cranial sutures. An amphiarthrodial joint is one having a fibrocartilaginous disk between the bony surfaces (symphysis), such as the symphysis pubis; or one with a ligament uniting the two bones (syndesmosis), such as the tibiofibular articulation. A diarthrodial joint is one in which the adjoining bone ends are covered with a thin cartilaginous sheet and joined by a joint capsule lined by a synovial membrane, which secretes synovial fluid. Synonym: arthrosis (1) See: illustrationMovementJoints are also grouped according to their motion: ball and socket (enarthrodial); hinge (ginglymoid); condyloid; pivot (trochoid); gliding (arthrodial); and saddle joint. Joints can move in four ways: gliding, in which one bony surface glides on another without angular or rotatory movement; angulation, occurring only between long bones, increasing or decreasing the angle between the bones; circumduction, occurring in joints composed of the head of a bone and an articular cavity, the long bone describing a series of circles, the whole forming a cone; and rotation, in which a bone moves about a central axis without moving from this axis. Angular movement, if it occurs forward or backward, is called flexion or extension, respectively; away from the body, abduction; and toward the median plane of the body, adduction. Because of their location and constant use, joints are prone to stress, injury, and inflammation. The main diseases affecting the joints are rheumatic fever, rheumatoid arthritis, osteoarthritis, and gout. Injuries comprise contusions, sprains, dislocations, and penetrating wounds. acromioclavicular joint Abbreviation: AC joint A gliding or plane joint between the acromion and the acromial end of the clavicle.amphidiarthrodial jointA joint that is both ginglymoid and arthrodial. ankle jointAnkle.arthrodial jointDiarthrosis permitting a gliding motion. Synonym: gliding jointball-and-socket jointA joint in which the round end of one bone fits into the cavity of another bone. Synonym: enarthrodial joint; multiaxial joint; polyaxial jointbiaxial jointA joint with two chief movement axes at right angles to each other.bilocular jointA joint separated into two sections by interarticular cartilage.bleeders' jointHemorrhage into joint space in hemophiliacs. Synonym: hemophilic jointBudin joint See: Budin jointcartilaginous jointA joint with cartilage between the bones. Charcot joint See: Charcot, Jean M.Chopart joint See: Chopart, FrançoisClutton joint See: Clutton jointcochlear jointA hinge joint permitting lateral motion. Synonym: spiral joint compound jointA joint made up of several bones. condylar jointEllipsoid joint.condyloid jointA joint permitting all forms of angular movement except axial rotation.cracking jointThe sound produced by forcible movement of a joint by contracting the muscles that contract or extend a joint, esp. the metacarpophalangeal joints. The cause is not known. See: crepitationcraniomandibular jointEither of the encapsulated, double synovial joints between the condylar processes of the mandible and the temporal bones of the cranium. The double synovial joints are separated by an articular disk and function as an upper gliding joint and a lower modified hinge or ginglymoid joint. Synonym: temporomandibular joint See: diarthrodial jointA joint characterized by the presence of a cavity within the capsule separating the bones, permitting considerable freedom of movement.dry jointArthritis of the chronic villous type. elbow jointThe hinge joint between the humerus and the ulna. ellipsoid jointA joint with two axes of motion through the same bone. Synonym: condylar jointenarthrodial jointBall-and-socket joint.facet jointAny of the zygapophyseal joints of the vertebral column between the articulating facets of each pair of vertebrae. false jointA false joint formation after a fracture. fibrous jointAny of the joints connected by fibrous tissue. flail jointA joint that is extremely relaxed, the distal portion of the limb being almost beyond the control of the will. ginglymoid jointA synovial joint having only forward and backward motion, as a hinge. Synonym: ginglymus See: hinge jointgliding jointArthrodial joint.hemophilic jointBleeders' joint.hinge jointa synovial joint in which two bones flex and extend in only one plane, usually because side (collateral) ligaments limit the direction of motion, e.g., elbow joint.hip jointA synovial ball-and-socket joint in which the head of the femur fits into the acetabulum of the hip bone. More than seven separate ligaments hold the joint together and restrict its movements. immovable jointSynarthrosis.intercarpal jointAny of the articulations formed by the carpal bones in relation to one another.irritable jointA recurrent joint inflammation of unknown cause. knee jointThe joint formed by the femur, patella, and tibia. midcarpal jointA joint separating the navicular, lunate, and triangular bones from the distal row of carpal bones.movable jointA slightly movable or freely movable joint, amphiarthrodial and diarthrodial, respectively.multiaxial jointBall-and-socket joint.pivot jointA joint that permits rotation of a bone, the joint being formed by a pivot-like process that turns within a ring, or by a ringlike structure that turns on a pivot. Synonym: rotary joint; trochoid jointplane jointA synovial joint between bone surfaces, in which only gliding movements are possible.polyaxial jointBall-and-socket joint.joint protectionA technique for minimizing stress on joints, including proper body mechanics and the avoidance of continuous weight-bearing or deforming postures.receptive jointSaddle joint.rotary jointPivot joint.sacroiliac jointThe articulation between the sacrum and the ilium of the hip bone. Joint movement is limited because of interlocking of the articular surfaces. saddle jointA joint in which the opposing surfaces are reciprocally concavoconvex. Synonym: receptive jointshoulder jointThe ball-and-socket joint between the head of the humerus and the glenoid cavity of the scapula.simple jointA joint composed of two bones.spheroid jointA multiaxial joint with spheroid surfaces. spiral jointCochlear joint.sternoclavicular jointThe joint space between the sternum and the medial extremity of the clavicle.stiff jointA joint with reduced mobility.subtalar jointAny of the three articular surfaces on the inferior surface of the talus.sutural jointAn articulation between two cranial or facial bones. synarthrodial jointSynarthrosis.synovial jointA joint in which the articulating surfaces are separated by synovial fluid. See: joint for illustalocrural jointAnkle.tarsometatarsal jointA joint composed of three arthrodial joints, the bones of which articulate with the bases of the metatarsal bones. temporomandibular jointCraniomandibular joint.trochoid jointPivot joint.ulnomeniscal-triquetral jointThe functional articulation of the distal ulna, articular disk, and triquetrum. The disk may subluxate following injury or with arthritis and block supination of the forearm. uniaxial jointA joint moving on a single axis.unilocular jointA joint with a single cavity.
acromioclavicular joint Abbreviation: AC joint A gliding or plane joint between the acromion and the acromial end of the clavicle.See also: jointFinancialSeeJoint |