The shoulder joint resembles a ball (humeral head) placed in a socket (glenoid fossa of the scapula). It is a joint with little snaps but on the other side is the most movable joint in the human body. This means that often it may suffer instability.
A shoulder is unstable when there is an abnormal and excessive movement between the humeral head and glenoid, ie when the humeral head is out of the socket. If the exit is total, it causes dislocation and if the exit is partial it causes a subluxation.
Shoulder instability can be:
- Traumatic: Traumatic instability is always caused by significant injury,such as in forced movements in throwing sports or swimming.
- Atraumatic: it may be multidirectional and caused by overuse of the arm in awkward and recurrent positions. The patient has the feeling that the shoulder ""comes out of place"" and is unstable in several directions.
