Most dislocations of the acromioclavicular joint are caused by direct violence. When the shoulder is landed or impacted, external forces are transmitted inwards along the shoulder and clavicle, causing damage to the acromioclavicular capsule, acromioclavicular ligament and rostral ligament, resulting in dislocation of the acromioclavicular joint, which may be accompanied by fractures of the acromion, clavicle and rostral process.