Problem: A female high school volleyball player consistently experiences pain when serving the ball overhand. She also indicates that it is worse when she spikes the ball. She has been diagnosed with shoulder impingement, and is on a rehabilitation program to strengthen her rotator cuff muscles. What is shoulder impingement? What structures are involved? Why is she on a rotator cuff strength program? Are there muscles other than the rotator cuff that she will likely need to strengthen as well?