1. Why does the acromion impingement sign occur when there is no shoulder impingement? In clinical practice, we often meet patients who ask, “I have no trauma to my shoulder joint, why do I have acromion impingement?” In fact, it is because there is osteophytes under the shoulder crest, which makes the gap between the shoulder crest and the greater tuberosity of the humerus smaller. The repeated and excessive use of the affected limb, especially the movement of the affected limb over the head, causes the shoulder crest and the greater tuberosity to collide, resulting in the soft tissue attached to the greater tuberosity, such as the supraspinatus tendon, being squeezed and rubbed. If the tendon fibers are worn for a long time, it can cause rupture of the tendon fibers, and if there is trauma, it can also cause instant rupture of the already worn tendon. Therefore, even if there is no impingement, you can still get acromioclavicular impingement, which is actually caused by bone and bone impingement, resulting in soft tissue injury such as rotator cuff secondary to a sterile inflammatory reaction. 2. What are the symptoms of acromioclavicular impingement? (1) Pain in the lateral shoulder, which is aggravated by movement and is more common at night, often affecting daily life; (2) Restriction of shoulder joint function, especially shoulder abduction and supination. In severe cases, the affected limb cannot comb the hair and wash the face, which hinders daily life. 3. How to diagnose acromioclavicular impingement syndrome? According to the patient’s symptoms such as shoulder joint pain, painful supination and abduction, etc., some physical examinations can be performed. A special X-ray can be taken to clarify the shape of the acromion. Ultrasound can be used to understand the condition of the subacromial bursa, but an MRI is needed to confirm the diagnosis. MRI is the main diagnostic tool for shoulder impingement, and its sensitivity and specificity are very high. 4. How to treat acromioclavicular impingement syndrome? (1) Conservative treatment: The two main problems of acromioclavicular impingement are pain and functional impairment. For pain, you can take oral NSAIDs, such as Cilobal, Acomplia, etc. Local closure of the subacromial impingement can be performed, active physical therapy, appropriate exercise, avoiding trauma, and paying attention to keeping the shoulder warm. (2) Surgery: Patients who have been treated conservatively for three months to six months without significant relief or even aggravation should undergo surgery. The selection of specific surgical indications should be based on the patient’s age, activity requirements, rotator cuff rupture site and other factors. The indications for surgery are stronger for younger patients and those with high activity requirements. Surgery is mainly performed to remove the impingement factor, decompress, clean up the inflammatory tissue, and suture the rotator cuff. There are two types of surgery: open incisional surgery and minimally invasive arthroscopic surgery. Open surgery is eliminated due to the large trauma, unsightly surgical incisions, patient reaction after surgery, and long recovery time. Arthroscopy is a rod-shaped optical instrument with a diameter of about 4 mm that is used to observe the internal structure of a joint. Arthroscopic surgery is a minimally invasive procedure with minimal pain and minimal postoperative reactions, and can be performed early after surgery to avoid complications such as long-term bed rest. The operation basically does not affect the muscle structure around the joint, and it can be used for early functional exercise after the operation to prevent joint stiffness and osteoporosis caused by long-term fixation of the joint. (3) Exercise after arthroscopy is very important: with functional exercise of the shoulder joint under proper guidance, more than 90% of patients can recover to 85% of normal shoulder joint function within 3 months. Pain and swelling will occur during the exercise period. With symptomatic treatment and proper guidance to adhere to the exercise, the symptoms will gradually ease or even disappear.