The rotator cuff. It consists of four muscles around the shoulder. These are the Subscapularis, the supraspinatus, the infraspinatus, and the Teres minor. These four muscles around your shoulder give you the wonderful motion and rotation of your arm over your head. These are muscles do things like allow you to reach the back of your head to comb your hair, things like reaching behind you to get your wallet out of your pocket, and even things like to scratch your back. Without these muscles, it becomes very difficult to do these things. These muscles encompass the whole shoulder. The subscapularis is in front and allows you to pull objects towards your body. The supraspinatus muscle is on top of the shoulder and it allows you to lift your arm up away from your body. The two Teres minor and infraspinatus are located more in the back of the shoulder and allow you to rotate your arm away from your body. These four muscles act in concert so that they all work together to give you this wonderful motion over your head.