Instability is a common cause of shoulder problems for people. This can vary from frank dislocations of the shoulder requiring reduction of the joint under an anaesthetic in hospital to subtle subluxations causing pain and dysfunction in your shoulder.
There are two major categories of shoulder instability; Traumatic & Multidirectional. The commonest instability pattern is Traumatic Anterior Dislocation. It is seen in patients who suffer an injury to their shoulder and dislocate out the front of the shoulder. These patients are often young males engaged in high impact sports. If they are young and remain active they will almost always redislocate their shoulders and usually they are troubled with recurrent dislocations. Modern treatment involves surgery to stabilise the shoulder and will usually be recommended after the very first dislocation.
Multidirectional instability is usually seen in people who are naturally very flexible. These people have what orthopaedic surgeons call ligamentous laxity which is a condition in which people have collagen that is more stretchy than normal. The shoulder may dislocate out the back or the front of the shoulder and has often done so since the patient was a teenager.