A shoulder separation occurs after a fall or a sharp blow to the top of the shoulder. It is usually sports related or happens in a car accident or fall. It is different from a shoulder dislocation because the dislocation occurs at the large joint where the arm attaches to the shoulder called the acromioclavicular joint (also called the AC joint). The AC joint is where the collarbone (clavicle) meets the highest point of the shoulder blade (acromion). The force of the injury is severe enough to tear the ligaments attaching to the underside of the clavicle. This causes the "separation" of the collarbone and wingbone. The wingbone actually moves downward from the weight of the arm. This creates a "bump" or bulge above the shoulder.