A traumatic instability around the shoulder joint may occur in two distinct places. A shoulder separation involves the acromioclavicular (AC) joint, where the clavicle or “collar bone” articulates with the top of the shoulder (acromion). A shoulder dislocation involves the true ball and socket of shoulder joint, the glenohumeral (GH) joint.
Shoulder separation describes various grades of injury to the ligaments which stabilize the acromioclavicular (AC) joint, resulting in a separation of the clavicle from the acromion. Shoulder separations usually are the result of a direct blow to the top of the shoulder, in a contact sport or an accidental fall.
Shoulder dislocation occurs when the ball of the shoulder joint is forced out of the socket (dislocation of the glenohumeral joint). As a consequence of injury to the ligaments and capsule that stabilize the joint, the patient may experience a range of symptoms - from a sense of looseness of the joint resulting in “slipping” and subluxation or partial dislocation, to recurrent complete dislocation of the joint.