The rotator cuff is a group of muscles with similar functions consisting of the supraspinatus, infraspinatus, teres minor and subscapularis muscles. The tendon portion of the four muscles forms a cuff-like structure at the anatomic neck of the humeral head, which surrounds the superior, posterior and anterior parts of the shoulder joint and is intertwined and fused with the shoulder capsule. The rotator cuff plays an important role in the stability of the shoulder joint. Rotator cuff injury is an important cause of shoulder pain and is a common clinical shoulder disorder. Features: 1. It is mostly seen in men over 40 years old, and if they are young, most of them have a history of serious trauma. 2. The affected limb has weakness in abduction and supination, and the shoulder may feel unstable. 3. Those with a long history of the disease may have atrophy of the shoulder muscles. Treatment: 1. Conservative treatment: Smaller tears and fresh tears can be tried conservatively. Rest and braking, non-steroidal anti-inflammatory drugs, topical drugs, closure, etc. 2.Arthroscopic surgery or open surgery to repair the rotator cuff is feasible.