The rotator cuff is a general term for the tendon tissue covering the subscapularis, supraspinatus, infraspinatus, and teres minor muscles in the anterior, superior, and posterior areas of the shoulder joint. The function of the rotator cuff is to bring the humeral head closer to the glenoid during upper arm abduction and to maintain a normal fulcrum joint between the humeral head and the glenoid. Injury to the rotator cuff will diminish or even eliminate this function, severely affecting upper extremity abduction. Trauma, degeneration and intra-articular impingement of the shoulder are common causes of rotator cuff injury. The disease is most often seen in patients over 40 years of age, especially those who are heavy workers. The shoulder is asymptomatic before the injury. After the injury, the shoulder has transient pain, which may gradually worsen and then turn into long-term chronic pain, and the pain is often worse at night. The patient is unable to lift the shoulder actively. When the rotator cuff is completely torn, it will seriously affect the shoulder joint abduction function due to the loss of its stabilizing effect on the humeral head. In partial rotator cuff tears, the patient can still abduct the upper arm, but there is mostly a 60° to 120° pain arc. Rotator cuff injury can be suggested by X-ray and magnetic resonance examination. For patients with early mild symptoms and imaging suggesting a small tear, conservative treatment can be attempted and the damaged tendon is expected to be repaired through rest and physical therapy. If the injury is severe and the rotator cuff is torn in its entirety, or if conservative treatment does not work well for 3 to 6 months, surgery is needed in a timely manner. With the development of arthroscopic technology, most rotator cuff injuries are now treated minimally invasively under arthroscopy with good results. For partial huge tears or poor conditions, small incision open surgery is feasible to repair the injured rotator cuff.