When the four muscles of the rotator cuff function normally, they hold the head of the humerus inside the shoulder socket. This stable compression allows the shoulder to move easily in so many directions.

Without this compressive stability, the head of the humerus can start to slide up and out of the socket. This movement is called migration. Eventually the head of the humerus comes up against the bottom of the acromion. The acromion is the piece of bone that comes across the top of the shoulder from the scapula (shoulder blade).

The patient has pain, loss of motion, and loses function. Many other changes occur inside the joint. Tiny pieces of cartilage break lose inside the joint. The lining of the joint called the synovium starts to thicken. Calcium crystals form, further damaging the joint and soft tissues.

Rotator cuff arthropathy can be treated with a conservative management program. Non-steroidal antiinflammatories and a rehab program with a physical therapist are advised. If this doesn't work, then surgery may be needed.