What Is The Rotator Cuff?
Before we understand what the rotator cuff is we need to understand how the shoulder is designed, and therefore why we need the rotator cuff.
The main shoulder joint is known as the glenohumeral joint, and it is a ball and socket joint. The ball is the humeral head (the top part of your arm bone) and the socket is the acromion (part of your shoulder blade). This joint is structurally very unstable though, as the socket is very small in comparison to the ball (picture a golf ball on a tee). However this small contact area enables us to have a large range of movement and use our arms for many complex tasks. In order for the shoulder to stay stable when it is so mobile it needs help which comes in the form of muscles, and in particular the rotator cuff.
The rotator cuff is a group of four small muscles that attach from your shoulder blade to the humeral head. Their primary job is to aid the stability of the shoulder by helping hold the ball in the socket during arm movements.
The four muscles also have individual functions alongside their combined stability role. The first of these is the supraspinatus, whose job it is to help lift the arm up from the side of the body (abduction). In particular it is responsible for initiating the lift prior to the bigger deltoid muscle taking over. This muscle is the most common rotator cuff muscle to get injured and it is often a part of the pathology in over 60’s presenting with shoulder pain. The second muscle is the infraspinatus which helps create outward rotation of the arm. This is the second most commonly injured rotator cuff muscle, with injuries occurring from sudden pulling movements of the arm. It is quite common to see this muscle injury in dog walkers when the dog pulls very suddenly on its lead causing a jolt to their owners shoulder.
The third muscle also aids in the outward rotation of the arm & is called the Teres minor. This muscle works in conjunction with the infraspinatus but also helps aid arm movements when the arm is horizontal. The fourth and last muscle is the subscapularis muscle, whose main function is inward rotation of the arm, but it also aids in pulling the arm down from an elevated position (adduction).
These four muscles are frequently injured due to sudden high load movements that the body hasn’t trained for. Classic examples are people who suddenly do a lot of throwing or racquet sports, or just lift something a lot heavier than they are used to. The rotator cuff is like any muscle in the body; it will atrophy (reduce in muscle bulk) and weaken without regular controlled use – such as strengthening exercises. When the rotator cuff weakens it is no longer able to hold the shoulder joint in a good position making any high loading activity a risk to injury.
To maintain a healthy shoulder complex, regular mobility and strengthening exercises are essential and also greatly reduce the chances of injury and pain.