High Quality Content by WIKIPEDIA articles! A separated shoulder (also known as acromioclavicular separation, AC joint separation, AC separation), is a common injury to the acromioclavicular joint. This is not to be confused with shoulder dislocation which occurs when the humerus separates from the scapula at the glenohumeral joint. The AC joint is located at the distal end of the clavicle, known as the acromial end, and attaches to the acromion of the scapula. Although this is part of the shoulder, a dislocation and a separation are completely different. Acromioclavicular separation occurs as a result of a downward force being applied to the superior part of the acromion, either by something striking the top of the acromion or by falling directly on it. The injury is more likely to occur if the shoulder is struck with the hand outstretched. Despite the scapula pulling on the clavicle during impact, the clavicle remains in its general fixed position because of the sternoclavicular joint ligaments.