A 'rotator cuff tear' is a tear of one or more of the tendons of the four rotator cuff muscles. A rotator cuff 'injury' can include any type of irritation or damage to the rotator cuff muscles or tendons. Rotator cuff tears are among the most common conditions affecting the shoulder. The cuff is responsible for stabilizing the glenohumeral joint and rotating the humerus outward (external rotation). When shoulder trauma occurs, these functions can be compromised. Since individuals are highly dependent on the shoulder for many activities, overuse of the muscles can lead to tears, with the vast majority again occurring in the supraspinatus tendon.