The consequence of subacromial impingement syndrome is rotator cuff tear. According to the damage of rotator cuff tissue, subacromial impingement syndrome can be divided into three stages: stage I is the period of rotator cuff edema and bleeding, stage II is caused by rotator cuff tendon, and stage III rotator cuff tear occurs. The clinical manifestation of subacromial impingement syndrome is shoulder pain, which is usually located on the lateral aspect of the acromion and sometimes radiates to the deltoid stop area. At the beginning of the disease, pain usually occurs during shoulder activity, especially during forward flexion and abduction, and is painless at rest. Due to the pain, some patients will feel weak force. If the pain is not significant and the force is diminished, it often suggests the presence of rotator cuff tear. In addition, some patients have a rattling sound in the shoulder during shoulder activity, and some have a feeling of interlocking, which is caused by subacromial bursitis and rotator cuff injury.