Impingement syndrome is a common disorder of the shoulder that refers to an improper alignment of the bones and tissues in the upper arm. Inflammatory conditions such as tendinitis, bursitis, and arthritis are all closely related to impingement syndrome, as are tears to the rotator cuff tendons.

If the rotator cuff becomes inflamed from overuse or there is a bone deformity or spur on the end of the shoulder blade, then the space between the upper arm bone and the tip of the shoulder blade is narrowed, causing the rotator cuff and its fluid-filled bursa to be squeezed or pinched. This impingement causes irritation and pain to the rotator cuff when the shoulder is raised.