Shoulder joint: The flexible ball-and-socket joint formed by the junction of the humerus and the scapula. This joint is cushioned by cartilage that covers the face of the glenoid socket and head of the humerus. The joint is stabilized by a ring of fibrous cartilage (the labrum) around the glenoid socket. Ligaments connect the bones of the shoulder, and tendons join these bones to surrounding muscles. The biceps tendon attaches the biceps muscle to the shoulder and helps stabilize the joint. Four short muscles that originate on the scapula pass around the shoulder, where their tendons fuse together to form the rotator cuff.
See also shoulder.