Common causes of acromioclavicular impingement syndrome include congenital factors, trauma, and degenerative changes. 1. Congenital factors: Congenital factors make the shoulder joint develop abnormally, resulting in the impingement of the proximal humerus and the acromion. 2. Trauma: Trauma such as strong impact makes the proximal tuberosity of humerus dislocated, and due to improper recovery, it leads to impingement of the acromion. 3. Degenerative changes: Degenerative changes in the shoulder joint lead to osteophytes, aggravated tendon wear and tear, and decreased rotator cuff muscle strength, which leads to acromioclavicular impingement. In life, you can prolong the time of shoulder lifting or add the weight on the hand appropriately, for example, you can hold a certain weight of dumbbells to carry out rehabilitation training. If there is any discomfort, it is recommended to go to the hospital in time.