A shoulder separation occurs after a fall or a sharp blow to the top of the shoulder. This injury is usually sports related. Some separations happen in car accidents or falls. This is not the same as a shoulder dislocation, which occurs at the large joint where the arm attaches to the shoulder, although the two may appear to be the same.
The shoulder separation, or acromioclavicular (AC) dislocation, is an injury to the junction between the collarbone and the shoulder. It is usually a soft-tissue or ligament injury but may include a fracture (broken bone).