Shoulder disorders are common in everyday life, especially in women around the age of 50. A distinctive feature of shoulder disorders is that they are almost always associated with pain. A common clinical condition that is mainly associated with shoulder pain is frozen shoulder, also known as frozen shoulder. It is also known as the “fifty shoulder” because of its tendency to occur in people around the age of fifty. Bursitis of the long head of the biceps muscle, supraspinatus fasciitis, and bursitis of the bursa near the shoulder joint are most common in subacromial bursitis and subdeltoid bursitis. The rotator cuff is a very important anatomical structure around the shoulder joint, so what is the rotator cuff? In fact, the rotator cuff refers to the supraspinatus, infraspinatus, teres minor and subscapularis muscles, as they wrap around the shoulder like a sleeve, also known as the rotator cuff of the scapula, and play an extremely important role in the function and stability of the shoulder. The supraspinatus muscle is in the rotator cuff and is the intersection of the forces concentrated around the shoulder. As a result, 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 motion. Rotator cuff injuries are usually treated by manipulation, but surgery is used for those with complete tendon rupture. Calcification of the rotator cuff is also a cause of shoulder pain. If the patient has suffered a mild or severe shoulder injury, it can produce supraspinatus syndrome with varying degrees of rupture of the tendon and mild tears of the soft tissue surrounding the joint capsule. A chronic injury can last for several months and calcification and deposits are formed in this way. Injury to the internal glenoid labrum can also cause prolonged pain in the shoulder joint and can only be diagnosed and treated with arthroscopic surgery. If the shoulder is not only painful but also swollen and the muscles are atrophied, you should be careful of tuberculosis of the shoulder joint. Tumors in the shoulder should be noted, such as osteosarcoma and fibrosarcoma, which have severe pain, especially at night, no relief, rapid progression, and poor prognosis. Some benign lesions, such as bone fibrous dysplasia, bone cysts, synovial chondromatosis, etc., can cause shoulder pain. If you have any of these conditions, you should take a film as soon as possible to clarify the diagnosis and treat the condition as soon as possible. There are also some systemic diseases that can cause shoulder pain, such as rheumatoid arthritis, polymyositis, rheumatism, etc. Certain metabolic diseases such as gout and osteoporosis can also cause shoulder pain. Some visceral diseases can also cause involved shoulder pain, such as cholecystitis, right subdiaphragmatic abscess, hepatitis, heart disease, pneumonia, etc., when the shoulder examination is negative. In conclusion, the causes of shoulder pain are many. If the pain does not improve after simple conservative treatment and worsens day by day, you should go to the hospital in time to see a doctor, so as not to delay the condition and to prevent the disease early and treat it early.