That person starts a lifting activity which exceeds the strength of the tendons, and the tendon tears acutely, leaving an inability to raise the arm. There may or may not be pain associated with the event. In some cases a rotator cuff may be only a partial tear of the tendons, and you may have pain but can continue to move the arm in a normal range of motion. In other cases, a complete rupture of the tendons occurs, and you are unable to move the arm in a normal range of motion. A complete rotator cuff tear usually results in an inability to raise tha arm away from the side under your own power.
Most people report an inability to sleep on the affected side, due to pain.
The physical examination can be very suggestive of a rotator cuff tear. A complete tear is usually very obvious. If your doctor can move the arm in a normal range of motion, but you are unable to move the arm using your own strength, there is a high likelyhood of a tear in the tendons. This test involves placing dye into the shoulder joint. Xrays are then taken to see if the dye leaks from the shoulder into the bursa.