Rotator Cuff Tear
The rotator cuff is the four tendons which control the movement of the shoulder. A tear in the rotator cuff can be caused when the narrow gap through which the rotator cuff passes becomes narrowed either due to a bony spike forming, or due to the thickening of a ligament. This causes increased pressure on the rotator cuff tendons, initially making them inflamed and painful.
If the pressure is not relieved, the tendons can become damaged and will ultimately tear. Usually, the uppermost tendon, the supraspinatus, tears first. If the tear gets worse, the next tendon, the infraspinatus, tears as well.