Unlike the knee which relies on ligaments for its stability, the shoulder has to make do with a set of four muscles known as the rotator cuff. These important muscles are responsible for defending the joint as well giving it a wide range of movement. It can be very easy to tear a rotator cuff muscle, and it's a common injury that affects around 2 million Americans every year. Fortunately, there's a lot you can do to repair a rotator cuff injury from home. Perhaps the most important step towards a full recovery is to make use of a specially designed shoulder sling or brace.