Left shoulder pain may be a sign of sports injury, frozen shoulder, cervical spondylosis, rotator cuff injury and other diseases. 1. Sports injury: If the patient has performed a strenuous shoulder exercise, it may cause the patient’s supraspinatus and infraspinatus muscles to be strained, which may lead to localized pressure points on the shoulder. In addition, if the shoulder or arm strength training, may also appear shoulder pain, usually rest for a few days can be relieved. 2. Frozen shoulder: If the left shoulder suffers from frozen shoulder, pain may occur. Frozen shoulder is usually manifested as radiating pain or pressure pain around the shoulder, and the patient may also have limited movement of the left shoulder joint, and the left shoulder may feel obvious restriction in abduction, posterior extension and anterior flexion. 3. Cervical spondylosis: cervical spondylosis can also cause left shoulder pain, such as nerve root cervical spondylosis, if the nerve of the left upper limb is compressed, the patient may have left neck and shoulder pain, which may be accompanied by weakness, soreness, numbness and other symptoms of the left arm. 4. Rotator cuff injury: If the rotator cuff of the left shoulder is injured, patients will have left shoulder pain, usually accompanied by weakness, and rotator cuff injury pain occurs in the upper arm and shoulder side and front, usually occurs during strenuous exercise. In addition, pain caused by angina pectoris and heart attack may also radiate to the shoulder. If the patient’s left shoulder pain is not significantly relieved after resting, it is recommended to go to the hospital in time for further examination and treatment.