Acromioclavicular popping is generally a normal physiological phenomenon, but it may also be caused by osteoarthritis of the shoulder joint, acromioclavicular bursitis and other disease factors. 1. Normal physiological phenomenon: acromion popping is mainly an audible sound or palpable vibration caused by the friction between the joint capsule or tendon and the scapula in the process of scapular movement or mobilization, which is a normal phenomenon. 2. Osteopathy of shoulder joint: this disease is mainly caused by the formation of local bone spurs, old fracture of humeral head of shoulder joint, cartilage injury, etc., which will lead to the symptom of rattling of the acromion during the activity due to the stimulation of adverse factors. 3. Acromioclavicular bursitis: it will cause part of the structures of the shoulder joint to friction and collision under the acromion, thus causing the acromion to pop. In case of shoulder popping, you should pay attention to reduce the weight-bearing activities of the shoulder joint and keep warm. If the snapping is accompanied by uncomfortable symptoms, you should consult a doctor to clarify the cause of the snapping.