n. a ball-and-socket joint: a type of *diarthrosis (freely movable joint), e.g. the shoulder joint and the hip joint. Such a joint always involves a long bone, which is thus allowed to move in all planes.
(synovial joint) n. a freely movable joint. The ends of the adjoining bones are covered with a thin cartilaginous sheet, and the bones are linked by a ligament (capsule) lined with *synovial membrane, which secretes synovial fluid (see illustration). Such joints are classified according to the type of connection between the bones and the type of movement allowed. See arthrodic joint; condylarthrosis; enarthrosis; ginglymus; saddle joint; trochoid joint.... diarthrosis
the ball-and-socket joint (see enarthrosis) between the head of the femur and the acetabulum (socket) of the ilium (see hip bone). It is a common site of osteoarthritis and rheumatoid arthritis, which is often treated surgically (by *hip replacement). See also congenital dislocation of the hip.... hip joint
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