The rotator cuff: biological adaptations to its environment.

The rotator cuff is a common source of shoulder pain in individuals who rely on overhead activities for work and sport. As diagnostic and treatment measures continue to advance, it is important for the physician to retain a knowledge of the anatomy and biological properties of the rotator cuff in its surroundings. The collagen composition, proteoglycan and glycosaminoglycan content, and cellular activity of the rotator cuff reflect its mechanical function. Also, the rotator cuff maintains fibrocartilagenous properties as it is under compression in its normal state. While many of these characteristics appear to be adaptive and occur in the healthy rotator cuff, some may predispose the tendon complex to pathology.