What is the Rotator Cuff?

What Is the Rotator Cuff?

First off, it is not the “rotary cup.” I actually hear it called that fairly often, but I usually let it slide.

The rotator cuff has one primary job. Its role is to hold the head of the humerus securely in the shoulder socket while the arm moves.

The shoulder socket itself is relatively shallow. Because of that, the shoulder joint does not get a lot of stability from the bones alone. Instead, it relies heavily on the surrounding muscles to keep everything in proper alignment.

The upside of this anatomy is that it gives the shoulder an incredible amount of mobility. It allows us to do things like swim a backstroke, throw a baseball, or reach overhead with ease.

The rotator cuff is made up of 4 muscles that originate on the shoulder blade and surround the head of the humerus. Together, they provide stability and help guide the shoulder through its full range of motion.

Let’s go through them one by one.

1. Supraspinatus

The supraspinatus sits above the spine of the scapula. The spine of the scapula is the ridge on the shoulder blade where several muscles attach.

The supraspinatus travels underneath the acromion and attaches to the top outer portion of the humerus. Its main job is to help lift the arm out to the side.

This is the most commonly strained or torn rotator cuff muscle.

2. Infraspinatus

The infraspinatus sits below the spine of the scapula and covers much of the back of the shoulder blade.

It attaches just behind the supraspinatus on the humerus. This muscle helps rotate the shoulder outward and assists with pulling the arm back.

3. Teres Minor

The teres minor attaches along the outer border of the scapula and travels upward to attach just behind the infraspinatus on the humerus.

Like the infraspinatus, this muscle helps rotate the shoulder outward. It also helps pull the arm down when the shoulder is elevated overhead.

4. Subscapularis

The subscapularis is unique because it sits on the front side of the scapula. It lies between the shoulder blade and the rib cage.

From there, it wraps around the front of the shoulder and attaches to the humerus underneath the pectoralis major. This muscle is responsible for rotating the shoulder inward, such as when accelerating the arm during a throw.

Each of these muscles has its own specific role, but they work best as a team. Their combined job is to keep the shoulder stable and allow the joint to move smoothly and safely.

I will link a video here that shows several exercises you can use to keep these muscles strong and healthy.

If you think you may be dealing with a rotator cuff issue, feel free to reach out. We would be happy to help you figure out what is going on.