Cartilage covers the ends of the bones.
The shoulder, the major joint in the upper extremity, is held together by muscles and capsular ligaments that allow your shoulder to position your hand in space to perform activities. There are seventeen muscles that coordinate the movement of the shoulder joint. Four of the major muscles form the deep layer of muscles known as the rotator cuff. When a shoulder becomes diseased or injured, simple movements can be painful and take the joy out of life. Most people want relief from the pain and disability caused by severe arthritis.