This is an injury of the acromioclavicular joint (commonly called the "AC" joint). This is the joint where the clavicle meets the scapula. A shoulder separation is a stretching or a tearing of the ligaments that support these bones. This allows the bones to move out of position.
A separated shoulder is most commonly caused by traumatic injury. It can happen if you fall on your shoulder, or if you are struck on the point of your shoulder. Athletes who play contact sports such as football and hockey are susceptible to this injury. So are skiers and gymnasts.
Symptoms may include pain and weakness in your shoulder. You may not be able to move your shoulder through its full range of motion. You may have bruising and swelling. Your shifted clavicle may create a visible bump beneath your skin.
Treatment options include rest, ice and medications. Your arm may be placed in a sling. You may benefit from physical therapy. A severe injury may require surgical repair. Your healthcare provider can create a care plan that is right for your needs.