Scapular instability is caused by trauma, chronic strain injury, or may be due to laxity of the joint capsule and surrounding muscle ligaments. 1. Trauma: Bone and soft tissue injury caused by shoulder trauma, or chronic strain injury of the shoulder, can affect the local muscle pulling and stabilization of the scapula, and then the manifestation of scapular instability. 2. Chronic strain: Frozen shoulder and other diseases can lead to chronic strain and adhesion of the muscles around the shoulder and the scapula, which will lead to limited movement and instability when the scapula moves. 3. Laxity of joint capsule and surrounding muscle ligaments: Congenital or traumatic laxity of the scapular joint capsule and ligaments around the scapula can lead to scapular instability. When scapular instability occurs, it is necessary to consult a doctor in a timely manner. Under the guidance of a specialized doctor, appropriate treatment can help to alleviate the uncomfortable symptoms as soon as possible.