What is the mechanism of injury of acromioclavicular separation?

Acromioclavicular separation results from a downward blow to the acromion. It is usually sports related. Injury may also be caused by applying traction to the arm or falling on the hand or elbow Acromioclavicular separation results from a downward blow to the acromion. It is usually sports related. Injury may also be caused by applying traction to the arm or falling on the hand or elbow with the arm flexed at a 90 degrees angle.