The diagnosis of subacromial impingement syndrome is based on history and signs. The first step is to examine the site of pressure pain, which is often located at the anterolateral border of the acromion, the biceps tendon groove and the acromioclavicular joint. Unless there is an acute injury, there is usually no localized redness or swelling. The supraspinatus tendon stop can be palpated at the anterior border of the acromion when the shoulder is internally rotated by posterior extension. Atrophy of the supraspinatus and infraspinatus muscles may occur in longer term cases. 1, Pain arc sign: high sensitivity. 2.Drawing impact test: X-ray studies confirm that the greater tuberosity of the humerus is no longer in contact with the acromion when the upper limb is drawn and then abducted. 3.Impingement evoked test includes Neer impingement sign and impingement test and Hawkins impingement sign. Orthopantomogram of the shoulder joint and supraspinatus exit radiographs are routinely taken. Typical changes include subacromial surface sclerosis and osteophyte formation, macronodular sclerosis, and cystic changes. The shape and thickness of the acromion can be evaluated by supraspinatus, which is classified by Bigliani into three types: type I (flat acromion), type II (curved acromion), and type III (hooked acromion), while ultrasound and MR examines structures such as the rotator cuff, biceps tendon, and glenoid labrum. The diagnosis of subacromial impingement syndrome can be made by meeting three of the following five criteria 1. pressure pain at the anterior and lateral edges of the acromion. 2, Positive pain arc sign during upper extremity abduction. 3. Pain is significant during active shoulder joint activity compared to passive activity. 4. Positive Neer impingement test. 5.Prominent acromion, partial or full rotator cuff tear. Treatment includes two main categories: non-surgical treatment and surgical treatment. All patients should be treated conservatively first. The methods and objectives of conservative treatment include: applying medication and physical therapy to eliminate the inflammation in the subacromial space; maintaining the normal range of motion of the joint through active exercise; and maintaining the normal strength of the shoulder muscles through strength exercises. The duration of conservative treatment should be determined by the severity of the symptoms, the patient’s occupation and the level of exercise, usually around three months. Medication includes oral non-steroidal anti-inflammatory and pain-relieving drugs, local topical medication and subacromial gap closure therapy, which should not be used more than three times. Some studies have shown that hormones can interfere with cellular metabolism and lead to atrophy of rotator cuff tendons and surrounding soft tissues. Physical therapy can be chosen from measures such as ultrashort wave. For patients in the acute stage, a neck and wrist sling or triangular scarf can be used for 1 to 2 weeks of braking, during which the full range of motion of the shoulder joint should be performed several times a day to avoid joint adhesions. If, after strict conservative treatment, the patient’s symptoms do not resolve, surgical treatment may be used. Surgery is performed using subacromial space decompression, including anterior acromioplasty, subacromial bursal resection, and removal of the acromioclavicular joint bones. If the degeneration of the acromioclavicular joint is severe, distal clavicle resection is feasible. After surgery, the affected limb is suspended in a neck and wrist sling or triangular scarf, and passive forward flexion exercises are started after 1 to 2 days, gradually increasing the angle, and active activities are started after 2 to 3 weeks.