Acromioclavicular Separation

What is it?

An acromioclavicular (uh-kro-mee-o-kluh-vik-u-ler) injury is an injury that causes the shoulder and collarbone to change position. These bones move or come apart because the ligament (tissue) that holds the bones in place is stretched or torn. This injury is caused by falling on your shoulder. Or you may be injured from a blow to your upper body. You may have pain, swelling, stiffness, or numbness. Or you may have problems moving the arm on the injured side.