The rotator cuff, also known as the rotator cuff, is a complex of tendons that surrounds the humeral head, with the subscapularis tendon in front of the humeral head, the supraspinatus tendon above it, and the infraspinatus tendon and the lesser circularis tendon behind it. . The supraspinatus is in the rotator cuff and is the intersection of the forces that are concentrated around the shoulder. Therefore, it is extremely vulnerable to damage. Especially when the shoulder is frequently abducted, the supraspinatus tendon is easily damaged by extrusion and friction, resulting in aseptic inflammation or tendon rupture because it passes through the narrow gap between the subacromial and humeral heads. The remaining infraspinatus, subscapularis and teres minor can also be injured, but the symptoms are more prominent in the supraspinatus tendon. Injury to these tendons and aseptic inflammation or rupture of the supraspinatus tendon is known as rotator cuff injury. After rotator cuff injury, patients often feel more pain in the lateral shoulder, and the pain increases during abduction. When the muscles of the rotator cuff are paralyzed, the shoulder joint must be dislocated. Calcification of the rotator cuff can cause shoulder pain and corresponding limitation of movement. The main symptoms: shoulder abduction pain and subacromial pressure pain. What are the clinical manifestations of rotator cuff rupture? (1) History of trauma: A history of acute injury, as well as a history of repetitive or cumulative injury, is informative for the diagnosis of this disease. (2) Pain and pressure pain: The common site is anterior shoulder pain, located in the anterior and lateral deltoid muscle. In the acute phase, the pain is severe and persistent; in the chronic phase, it is spontaneous dull pain. The symptoms worsen after shoulder activity or after increasing the load. The pain is also aggravated by passive external rotation of the shoulder joint. Nocturnal worsening of symptoms is a common clinical manifestation. Compression pain is usually found in the proximal aspect of the greater humeral tuberosity, or in the subacromial space. (3) Functional impairment: In large rotator cuff ruptures, active shoulder supination and abduction are limited. The range of abduction and forward elevation is less than 45°. However, the passive range of motion is not significantly limited. (4) Muscle atrophy: If the history of the disease is more than 3 weeks, there are different degrees of atrophy of the muscles around the shoulder, with the deltoid, supraspinatus and infraspinatus muscles being more common. (5) Secondary contracture of the joint: If the disease duration is more than 3 months, there are different degrees of limitation in the range of motion of the shoulder joint, and the limitation of abduction, external rotation and supination is more obvious. (6) Special signs: a. Shoulder drop test: If the affected arm is passively elevated to 90°-120° of supination and the support is removed, the arm drop and pain occurs when the affected arm cannot be supported on its own is considered positive. b.Impact test: Press downward on the shoulder peak while passively raising the affected arm, if there is pain in the subacromial space or if there is inability to raise the arm, it is positive. c. Pain arc sign: A positive test is when there is pain in the anterior shoulder or subacromial region within 60°-120° of the affected arm, which is diagnostic for rotator cuff contusion and partial tears. d.Friction sound in the glenohumeral joint: the sound of friction or gravel sound in the glenohumeral joint during active or passive activities, often caused by scar tissue at the rotator cuff break. If the patient can actively abduct the rotator cuff after anesthesia, it indicates that the rotator cuff is not torn or only partially torn. If the rotator cuff cannot be actively abducted after closure, it indicates a severe rotator cuff tear or complete rupture. （MRI is a non-invasive test that can detect rotator cuff injury. Most partial rotator cuff ruptures do not require surgical treatment and can be fixed in a cast or abductor brace for 3-4 weeks and then functional exercises can be started. In elderly people, immobilization is generally not advocated to prevent the occurrence of frozen shoulder and early functional exercise when the pain is tolerable. For 4-6 weeks conservative treatment is not effective surgery can be considered to repair the damaged rotator cuff. In cases of complete rotator cuff rupture that cannot heal on its own, surgery should be performed as early as possible except for patients who are too old and frail to tolerate surgery, usually within three weeks after the injury. The surgical options are minimally invasive arthroscopic surgery and arthroscopically assisted minimally invasive rotator cuff repair surgery.