Rotator cuff is a muscle group surrounding the shoulder joint, including supraspinatus, infraspinatus, subscapularis, and teres minor. The rotator cuff is closely related to the movement of the shoulder joint, and if the rotator cuff is injured, pain, weakness, and dyskinesia will occur in the shoulder joint, etc. The following introduces the characteristics of rotator cuff injuries and their treatments: Symptoms and Signs: 1. Repeated and persistent pain, especially during lifting activities. 2.Night pain, the affected side lying on the side affects the sleep. 3.Muscle weakness, especially when trying to lift the arm. 4. Friction or popping sensation when moving the arm. 5. Restriction of shoulder joint movement. 6. The pain usually occurs on the side with more activity. 7. Pain may be triggered by a specific activity. Risk factors: 1. Repeatedly doing activities that raise the arm, such as laying tile or painting ceilings. 2, When lifting heavy objects. 3, Trauma such as falling. 4, Aging of the shoulder joint, the blood supply to the rotator cuff is reduced. 5. Narrowing of the space between the clavicle and the acromion. Wear and tear of the humeral head on the surface of rotator cuff. Diagnosis of rotator cuff injury: 1. Occupation, symptoms and history of trauma. 2. 2, Are the muscles around the shoulder joint atrophied? The mobility of the shoulder joint, the location of activity limitation. 3.Signs of acromioclavicular impingement as well as some other shoulder joint special examination. 4.Taking X-ray film to understand the bone condition and the shape of the acromion. 5.Arthrography 6.MRI(Nuclear Magnetic Resonance Imaging)(The standard of diagnosis). 7, Ultrasonography, etc. Treatment: Rotator cuff injury may be partial or complete. Partial rotator cuff injury can be treated non-operatively and complete rotator cuff tear requires surgery. Surgery should also be considered for incomplete rotator cuff injuries when conservative treatment is ineffective. Most of the rotator cuff injuries are relieved after conservative treatment, and the following conservative treatments are mainly available: 1. Rest. 2.Non steroidal anti-inflammatory drugs can relieve pain. 3.Corticosteroid intra-articular injection. 4, ultrasound can synergize the effect of drug therapy, and there is a thermal effect with auxiliary efficacy. 5.Functional exercise of shoulder joint. Surgical treatment: 1, according to the size, depth and location of rotator cuff injury, different surgical methods can be adopted. 2.Surgical treatment under shoulder arthroscopy. 3.Minimally invasive surgical treatment with combined shoulder arthroscopy and small incision. 4.In case of severe rotator cuff injury, open surgical reconstruction is needed. 5.Artificial shoulder joint replacement.