Shoulder bone crunching when moving may be caused by normal physiological reasons, but also may be caused by periarthritis, old injury, acromioclavicular joint dislocation and other pathological reasons, should be timely consultation to find out the cause of the disease. 1. Physiological reasons: rattling of shoulder bones, mostly due to friction between the soft tissues around the shoulder joint and the shoulder joint during exercise. If there is no other discomfort in the body, there is usually no need for special treatment. 2. Frozen shoulder: mainly refers to the chronic specific inflammation of the shoulder joint capsule and its surrounding ligaments, tendons and synovium, which is caused by long-term hyperactivity, poor posture, improper treatment after traction injuries and other factors. It can make the shoulder joint activities in all directions and passive activities are limited, then there will be shoulder bones crunching when you move. 3. Synovial hyperplasia: If the patient has more synovial hyperplasia in the shoulder joint, synovial hyperplasia will be formed. When the shoulder joint moves, the synovial membrane collides with the cartilage of the humerus, and the shoulder bone will rattle when it moves. 4. Acromioclavicular joint dislocation: In addition, acromioclavicular joint dislocation can also lead to shoulder bone crunching sound when moving, accompanied by pain, joint activity restriction and other symptoms. Shoulder bones crunching on movement may also be caused by other reasons, such as calcium deficiency, cervical spondylosis, and so on. It is recommended that the patient go to a regular hospital in time, after identifying the cause, under the guidance of the doctor to carry out targeted treatment.