Joint - definition and function

Joint - An articulating structure that connects two or more BONE surfaces to allow movement. The movement may be slight or the joint fused, such as the sutures in the cranium (skull). A joint may function like a hinge, such as the knee and elbow, or like a ball and socket, such as the hip and shoulder. In the carpal (hand) and tarsal (foot) joints, the bones glide along each other. Synovial capsules enclose joints that allow extensive movement between the bone surfaces, such as the knees, hips, and shoulders. The synovial membrane produces synovial fluid, which lubricates the bone ends within the joint to reduce friction between or among the structures of the joint during movement. Joints are particularly vulnerable to injury and damage resulting from repetitious motion.

For further discussion of joints within the context of the structures and functions of the musculoskeletal system, please see the overview section “The Musculoskeletal System.”

See also BURSA; JOINT REPLACEMENT; LIGAMENT; MUSCLE; OSTEOARTHRITIS; TENDON.

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