Frozen shoulder should be differentiated from the following diseases that cause shoulder pain: 1. Rotator cuff injury: 70% of shoulder pain is caused by rotator cuff injury, which requires an MRI to confirm the diagnosis; 2. Shoulder impingement syndrome and subacromial bursitis can also cause shoulder pain; 3. If periarthritis pain occurs on the left side, radiating pain caused by heart disease should be excluded. If periapical pain occurs on the right side, radiation pain caused by cholecystitis or gallstones should be ruled out. In addition, radioactive pain caused by cervical spondylosis should be excluded.