What Is an AC Joint Injury (Separated Shoulder)?
Acromioclavicular(AC) joint injuries (also known as a separated shoulder) occur when the clavicle is forcefully dislocated from the acromion and is usually caused by a direct blow to the shoulder or falling on an outstretched arm.
There are varying degrees of severity in AC joint injuries and are classified into three categories.
- Type I: The AC ligament is slightly torn, but there’s no damage to the other ligaments.
- Type II: A partial dislocation of the joint and complete tearing of the AC ligament with little or no damage to other ligaments.
- Type III: Complete separation of the joint. The AC ligament, other ligaments, and the joint capsule are torn. Displacement of the joint is visible on an exam.
Without the ligament support, the shoulder drops from the weight of the arm and the clavicle is pushed upward causing a noticeable bump on the top of the shoulder.