What are the Rotator Cuff Muscles? - Definition & Actions

Instructor: Justine Fritzel

Justine has been a Registered Nurse for 10 years and has a Bachelor's of Science in Nursing degree.

Your body is made up of many different muscles that work to allow you to move in all sorts of ways. In this lesson, we will learn about the rotator cuff muscles and what they do.

Carrying the World on your Shoulders

We take for granted how ingeniously our body is designed. When we reach up to get something off the shelf, we do not even stop to think about all the intricate pieces working together to allow us to do this.

Imagine if you didn't have a moving joint in your shoulder. You wouldn't be able to reach that snack from the top shelf. You would not be able to pick up the glass of water on the table in front of you. And you definitely could not swing an axe to chop wood. If your shoulders did not have range of motion, your arms would essentially be useless. Our arms would be as pointless as the arms of a T-rex!

Although most of us can use our shoulders easily, there is quite a sophisticated design that allows these movements to be possible. Your shoulder blades, or scapulas, are located on your upper back. Your humerus is the long bone of your upper arm. The end of the humerus is near the scapula to make a shoulder joint. But two bones next to each other have no movement unless they have muscles to connect them together.

Let's look closer at the shoulder joint to see how it moves!

What is a Rotator Cuff?

Your rotator cuff is a group of muscles in your shoulder joint that hold your humerus securely in place in your shoulder socket. The rotator cuff muscles start at the scapula and attach to the humerus with tendons.

Rotator Cuff
Rotator cuff

Your rotator cuff is made up of four different muscles. Let's look at each of those muscles next and see how they work.

Supraspinatus Muscle

The supraspinatus muscle is the top most muscle that makes the rotator cuff. Supra means above which can help you remember the supraspinatus muscle is above the other rotator cuff muscles. This muscle is responsible for helping to bring the arm up away from the body. When the arm moves away from the body it is called abduction.

Have your arm hang at your side. Now lift it straight up to the side. This is abduction and the suprastinus muscle just helped you to lift your arm.

Infraspinatus Muscle

Next is the infraspinatus muscle. This muscle helps to stabilize the humerus. It helps you to rotate your arm laterally, or to the side.

Hang your arm at your side again with the palm of your hand towards your thighs. Move your hand up to make a 90 degree at your elbow. Now move your hand out to your side. You just used your infraspinatus muscle!

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