Is made up of four separate muscles, namely, the supraspinatus, infraspinatus, teres minor & the subscapularis. Most commonly it’s the supraspinatus that causes us the most problems and pain with the shoulder, it sits over the top of the joint and therefore the tendon can become trapped and inflamed.
You may have heard of the phrase “painful arc syndrome“, this usually refers to an impingement of a damaged tendon or alternative structure within the shoulder joint and is normally felt when you move your arm out to the side.