1, rotator cuff injury The rotator cuff includes the supraspinatus tendon, infraspinatus tendon, subscapularis tendon and the lesser circularis muscle, while rotator cuff injury usually refers to the supraspinatus tendon injury. The supraspinatus muscle is in the rotator cuff and is the intersection of the forces concentrated around the shoulder. It is therefore highly susceptible to damage. Especially when the shoulder is abducted frequently, the supraspinatus tendon crosses the narrow gap between the subacromial and humeral head, so it is easily damaged by extrusion and friction, resulting in aseptic inflammation or tendon rupture. 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 motion. In the past, rotator cuff injury tears required incision surgery, which was usually very traumatic and difficult for patients to recover; currently, minimally invasive treatment of rotator cuff tears under shoulder arthroscopy is the best means and the most cutting-edge method to treat this disease, with little surgical trauma and fast recovery for patients. 2. Recurrent shoulder dislocation Shoulder dislocation is most common in young, athletic people. The younger and more active the patient is when the dislocation first occurs, the more likely it is to develop into a habitual shoulder dislocation, or recurrent shoulder dislocation, or more accurately, traumatic shoulder instability. For example, patients who have their first shoulder dislocation in their teens have a 90% or greater chance of developing recurrent shoulder instability, and patients who have their first shoulder dislocation at age 40 or older are less than 10% likely to develop chronic shoulder instability. The shoulder joint consists of the articular pelvis, the humeral head, and the surrounding shoulder capsule and ligaments. The common cause of dislocation is anterior shoulder dislocation, which is caused by a fall on the arm that is abducted and strongly forced over the top, a direct blow to the shoulder, or a strong forced external rotation of the arm; the less common cause is posterior shoulder dislocation, which is often associated with seizures or electric shocks, when the muscles in the shoulder are strongly contracted, causing dislocation. Habitual shoulder dislocation (or traumatic shoulder instability) begins with the first shoulder dislocation, which damages the ligaments that support the shoulder joint. The surface of the articular glenoid is relatively flat and is deepened by the glenoid labrum, a cartilaginous cup that can wrap around part of the humeral head. The glenoid labrum acts as a bumper to hold the humeral head firmly in place in the glenoid, and it is also the attachment point for stabilizing the shoulder ligaments. When the glenoid labrum is torn from the glenoid, the support of these ligaments ceases to exist. The development of traumatic shoulder instability is inextricably linked to the type and extent of damage to the glenoid labrum and surrounding ligaments.