Like most orthopedic conditions, the most common mechanisms of a rotator cuff injury are separated into 'repetitive use' and 'traumatic.'

Repetitive Use Injury
In repetitive use injuries to the rotator cuff, repeated activities cause damage to the rotator cuff tendons. Over time, the tendons wear thin and a tear can develop within the tendons of the rotator cuff. Patients with repetitive use injuries to the rotator cuff often have complaints of shoulder bursitis prior to developing a tear through the rotator cuff tendons.

Traumatic Injuries
Traumatic injuries to the rotator cuff are seen after events such as falling on to an outstretched hand. The traumatic event can cause a rotator cuff injury by tearing the rotator cuff tendons. This type of injury can often occur when someone in a car accident uses their arm to brace themselves right before impact. While traumatic injuries are much less common than repetitive use injuries, however, when a rotator cuff tear occurs in a patient younger than 60 years old it is usually a traumatic injury.