Rotator cuff tears are caused by a number of different reasons, including morphological abnormalities of the coracoacromial arch, impaired blood circulation, overuse, and degenerative changes to the ligaments and tendons. The supraspinatus is most vulnerable to tears caused by repeated physical pressure exerted between the acromion and the humeral head. (Typically this injury occurs to professional athletes who often overuse their shoulders) Symptoms include shoulder joint pain, muscle atrophy, limited range of motion, and nyctalgia (pain at night). In the case of a complete tear, patients can no longer lift their injured arm above their head.