The rotator cuff is four muscles and their tendons. These combine to form a “cuff” over the upper end of the arm. The rotator cuff helps lift and rotate the arm and stabilize the shoulder joint. Rotator cuff tears are most common in people over the age of 40. They can occur in younger patients following trauma, repetitive overhead work, or sports activities. Symptoms include pain in the shoulder that radiates down the side of your arm, weakness, difficulty with overhead activities, and pain lying on the affected side at night. Treatment can entail rest, therapy, or surgery.