The rotator cuff is a group of four muscles and their associated tendons, that wrap around to form a “cuff” over the upper end of the arm at the shoulder. The rotator cuff helps guide the shoulder through motions by allowing lift and rotation to the arm while stabilizing the ball of the shouldert. The space above the top of the rotator cuff is occupied by a bursa. The bursa is a fluid sac between the tendon and the acromion bone. Bursitis is inflammation of this fluid sac and occurs due to repetitive overhead activity or overuse of the arm. The term impingement is used to reference pinching of the rotator cuff tendons and bursa against the acromion bone.