Shoulder instability occurs when the tissues in the shoulder become torn or stretched allowing the ball of the shoulder joint to move out partially or completely from the socket.
The ball of the shoulder joint is the head of the humerus bone or your upper arm and is ideally, supposed to rest in a socket in your shoulder blade.
Partial shoulder instability is associated with subluxation. The humerus head slides in and out of the socket quickly. It may be associated with pain or a “dead arm” sensation.
Some patients may not feel pain, but the instability just stops them from carrying out their normal activities.
Complete shoulder instability is also referred to as shoulder dislocation. Here, the humerus head glides out completely from the socket. Most times, physical therapy or medical assistance is needed to put the shoulder in place.
Instability of the shoulder can be to the front (anterior instability), to the back (Posterior instability), or in more than one direction (multidirectional instability). Anterior instability is the most common form of shoulder instability.