Even though the supraspinatus is the most commonly injured muscle of the four muscles in the rotator cuff, the other three muscles that comprise the rotator cuff, the infraspinatus, teres minor, and subscapularis, may also be injured. The cuff is responsible for stabilizing the glenohumeral joint, abducting, externally rotating, and internally rotating the humerus. When shoulder trauma occurs, these functions can be compromised. Because individuals are highly dependent on the shoulder for many activities, overuse of the muscles can lead to tears, the vast majority again occurring in the supraspinatus tendon.
Signs and symptoms
Many rotator cuff tears are have no symptoms. Both partial and full thickness tears have been found on post mortem and MRI studies in those without any history of shoulder pain or symptoms. However, the most common presentation is shoulder pain or discomfort. This may occur with activity, particularly shoulder activity above the horizontal position, but may also be present at rest in bed. Pain-restricted movement above the horizontal position may be present, as well as weakness with shoulder flexion and abduction.