Internal impingement is a specific type of shoulder injury that is seen primarily in throwing athletes. Internal impingement consists of injury to the following structures:
- The posterior labrum
The labrum in the posterior-superior region of the shoulder is often frayed or partially torn. In more severe cases, the tear can extend up towards the attachment of the biceps tendon, a so-called SLAP tear.
- The rotator cuff
The rotator cuff is partially torn on its undersurface. The type of tear is called a partial thickness rotator cuff tear--not a complete tear of the rotator cuff.
The problem is caused from pinching of the tuberosity (top of the humerus) against the labrum. Patients with internal impingement characteristically lack internal rotation--the ability to fully rotate the shoulder inward.