Shoulder pain when extending the arm back to a certain angle may be caused by physiological reasons such as muscle spasm, or it may be caused by pathologic reasons such as frozen shoulder, trauma and shoulder joint diseases. 1. Muscle spasm: due to muscle spasm at the shoulder joint caused by bad posture or cold, patients may have shoulder pain when their arms are stretched back to a certain angle. 2. Frozen shoulder: due to long-term shoulder joint strain caused by ligaments and other soft tissues of aseptic inflammation, which can lead to arm back to a certain angle shoulder pain. 3. Trauma: due to the injury to the shoulder joint, muscles, ligaments and other tissues, the patient may experience pain, swelling, limited activities and other symptoms, and the shoulder hurts when the arm is stretched back to a certain angle. 4. Shoulder joint diseases: such as shoulder joint infection, rheumatism, rheumatoid arthritis, osteoarthritis, shoulder joint tuberculosis, shoulder joint tumors and other diseases, patients can have shoulder pain when their arms are stretched back to a certain angle. 5. Cervical spondylosis: due to cervical degeneration compression of the nerve root, can cause patients to appear arm back to a certain angle shoulder pain, can also cause upper limb numbness, pain and other clinical manifestations. The arm back to a certain angle shoulder pain in a timely manner to the hospital, a clear reason to give targeted treatment.