Many middle-aged and elderly people often complain about shoulder pain or stiffness during activities. They have the same complaints and symptoms. When the shoulder joint moves to a certain angle, they will feel pain or weakness, and their arms can't be lifted. When they sleep at night, they often wake up in pain and can't lie on their side. The pain lasted for more than a year. During the period, he was treated as "scapulohumeral periarthritis" in many hospitals, but he was cured for a long time. They have done massage, physical therapy, Chinese medicine, acupuncture and sealing. After each exercise, the pain gets worse and the situation continues to deteriorate. After careful examination, they all suffered from the same kind of injury-"rotator cuff injury". The rotator cuff, which is characterize by pain and weakness of that shoulder joint, is a general term for the four tendon in the shoulder joint, and they wrap around the humeral head in a sleeve shape. The rotator cuff is located between the acromion and the humeral head. Its main function is to help the stability and movement of the shoulder joint, protect the humeral head from being pulled up by the deltoid muscle and avoid colliding with the acromion. This is a very important structure. However, rotator cuff is also a kind of tissue that is easy to be damaged and torn. Rotator cuff injury is very common in elderly patients over 60 who complain of shoulder pain, and the prevalence rate is as high as 70%, which is much higher than the so-called "scapulohumeral periarthritis". In the past, due to the limitation and misunderstanding of this kind of disease, most patients were misdiagnosed as "scapulohumeral periarthritis", which caused treatment mistakes and patients' pain. There are many diseases that cause shoulder pain, including rotator cuff tear, acromion impact, coracoid process impact, scapulohumeral periarthritis, sternoclavicular joint disease, pat injury, shoulder instability, tendonitis, calcified tendonitis on the job, cervical spondylosis, thoracic outlet syndrome and so on. This requires specially trained experts and very strict differential diagnosis ability. The mechanism of rotator cuff injury can be divided into acute tearing injury and chronic strain injury. Acute laceration is common in carrying heavy objects, shoulder support when falling, violent pulling by external force, etc. For example, a passenger standing on a bus with a pull rod suddenly loses his balance when braking, which may cause rotator cuff tear. Chronic strain is often caused by falling, upper limbs supporting the ground or lifting heavy objects hard. Regular exercise, shoulder strain, or excessive use of upper limbs; It is also common for people who have been engaged in tennis, baseball, badminton, swimming, mountaineering and other sports that need to lift their upper limbs above their heads for a long time. The rotator cuff injuries are mainly characterized by shoulder abduction and lifting pain. Due to the weakness of shoulder joint lifting, the severely injured shoulder needs the help of the opposite hand to complete the lifting action, and sometimes the shoulder joint movement may be slightly limited. Functional exercise is not helpful to relieve the pain of rotator cuff tear. If it is mistaken for "scapulohumeral periarthritis", let the patient with rotator cuff tear continue to do exercises such as "climbing the wall", or release the shoulder joint artificially, it may lead to the rotator cuff tear continuing to expand, and eventually form a huge or irreparable rotator cuff tear, which will aggravate the injury. This is a disease with high disability rate and should be paid attention to.