Shoulder instability occurs when the head of the upper arm bone is forced out of the shoulder socket. This can happen as a result of a sudden injury or from overuse.
Shoulder dislocations can be partial, with the ball of the upper arm coming just partially out of the socket. This is called a partial dislocation. A complete dislocation means the ball comes all the way out of the socket.
Once the ligaments, tendons, and muscles around the shoulder become loose or torn, dislocations can occur repeatedly.
Recurring dislocations, which may be partial or complete, cause pain and unsteadiness when you raise your arm or move it away from your body. Repeated episodes of dislocations lead to an increased risk of developing arthritis in the joint.