The Anatomy of the Rotator Cuff

Your rotator cuff is made up of four muscles: the supraspinatus, infraspinatus, teres minor, and subscapularis. The muscles start on the shoulder blade (scapula) and join as tendons to form a thick covering at the top of the humerus (the bone in the upper arm).

The rotator cuff has several important jobs, including stabilizing the shoulder, elevating and rotating the arm, and ensuring the head of the humerus stays securely placed in the shoulder socket.

This article will go over the anatomy and function of the rotator cuff muscles, how they get injured, and what to do if you hurt your rotator cuff.

Anatomy

The acronym SITS is often used as the name for the collection of muscles that make up the rotator cuff: supraspinatus, infraspinatus, teres minor, and subscapularis.

The four muscles of the rotator cuff are:

• Supraspinatus. The supraspinatus muscle originates above the spine of the shoulder blade and inserts on the greater tuberosity of the humerus.
• Infraspinatus. The infraspinatus muscle originates below the spine of the scapula in the infraspinatus fossa. It inserts on the posterior aspect of the greater tuberosity (the part of the bone that attaches to the corresponding muscle) of the humerus.
• Teres minor. The teres minor muscle originates on the lateral scapula border and inserts on the inferior aspect of the greater tuberosity of the humerus. The teres major muscle is not part of the rotator cuff.
• Subscapularis. The subscapularis muscle originates on the anterior, or front surface, of the scapula, sitting directly over the ribs, and inserts on the lesser tuberosity of the humerus.

Function

Each rotator cuff muscle performs a specific, important job that helps your shoulder joint work. 

Your rotator cuff:

• Stabilizes the head of the humerus in the shoulder joint. The supraspinatus, infraspinatus, teres minor, and subscapularis muscles all work together to keep the joint stable. 
• Abducts (elevates) the shoulder joint out to the side. These motions are done by the supraspinatus.
• Externally rotates the shoulder joint. The infraspinatus and teres minor muscles are responsible for these movements.
• Depresses the head of the humerus. The subscapularis muscle does this to allow the humerus to move freely in the shoulder joint when the arm is raised.

All four rotator cuff muscles work together to centralize your humerus bone in the shoulder joint. When you lift your arm, your rotator cuff muscles pull the joint together to stabilize your shoulder.

Since these muscles are so involved in the movement and stabilization of the shoulder, they can get worn out and even tear if the arm is used a lot or if it is injured in some way.

Associated Conditions

Sometimes, shoulder pain can come on for no apparent reason. 

Wear and tear of the rotator cuff and shoulder joint can happen with repetitive stress and postural neglect. When this happens, different structures around the rotator cuff are affected. 

If you have injured your rotator cuff, you may have pain or weakness when lifting your arm. A rotator cuff injury can also cause difficulty with basic functional activities like lifting, reaching, or sleeping.

Common injuries to the four rotator cuff muscles are:

• Rotator cuff tear
• Rotator cuff tendonitis
• Shoulder impingement
• Shoulder bursitis
• Shoulder labrum tear
• Shoulder separation

Any problems around your shoulder can cause limited motion and function.

However, some people have rotator cuff tears that show up on magnetic resonance imaging (MRI), but they have no pain, loss of strength, or limited function. Thus, the presence of a rotator cuff tear does not necessarily mean that you will experience problems with your shoulder.

Risk Factors for Rotator Cuff Injuries

There are certain motions and activities that increase your chances of getting a rotator cuff injury, including

• Performing overhead tasks
• Repetitive stress to your shoulder joint, as in throwing and racquet sports
• Contact sports
• Sitting with a rounded shoulder posture
• Failing to maintain general physical fitness

Lifting heavy objects or moving your shoulder the wrong way can cause a rotator cuff tear. However, most rotator cuff tears are from the tendons wearing down with age.

Repeatedly using the muscle for the same motion can make this type of tear more common.

A car accident, fall, or another sudden trauma to the shoulder can also cause a rotator cuff injury.

Working on keeping your joints healthy, avoiding overhead and repetitive strain on your shoulders, and maintaining proper posture can help you avoid painful shoulder injuries.

Rehabilitation

Depending on the severity of a rotator cuff injury, the treatment can range from simple rest and immobilization to surgery.

At home, resting your shoulder and doing heat therapy can help manage your symptoms. Even something as simple as taking a hot shower may help with the pain because it relaxes the shoulder and back muscles.  

You can also use an ice pack for 20 minutes a few times a day to help with swelling, just make sure you wrap ice in a towel so it is not directly on your skin.

Without surgery, it can take about a year for a torn rotator cuff to heal. About 20% of people who do not have surgery have ongoing pain or shoulder problems. If your rotator is surgically repaired, recovery can take 12 to 18 months.

Recovery from surgery to repair a torn rotator cuff can be slow, so orthopedic surgeons tend to shy away from doing these procedures. They may recommend them for younger patients, major tears, or older patients who have jobs that depend heavily on shoulder function.

When rotator cuff problems cause shoulder pain, you may benefit from working with a physical therapist (PT). Not only can they help figure out the cause of your shoulder pain, but they can also work with you on restoring normal shoulder range of motion (ROM) and strength.

Your PT will ask you questions about your shoulder pain and may do special tests on your shoulder to determine what structures are causing your symptoms. 

Treatment for a rotator cuff injury can involve different therapies to control pain. Shoulder exercises will likely be prescribed to help you restore normal mobility of the joint.

Exercises that can help you heal from a rotator cuff injury include:

• Shoulder range of motion exercises
• Scapular stabilization exercises
• Isometric shoulder strengthening
• Rotator cuff strengthening with resistance bands

Your PT can teach you what to do now to treat your rotator cuff problem, as well as show you how to prevent future problems with your rotator cuff muscles. 

Talk to your healthcare provider before starting any rotator cuff exercise program. Stop any exercise that causes acute pain or discomfort in your shoulder.

How Can I Prevent Rotator Cuff Injuries?

You can’t always avoid a rotator cuff injury, but there are some steps you can take to take care of your rotator cuff and make problems less likely to happen.

• If you have a job or hobby that relies on using your shoulder, always use proper form and technique to protect against injury. Rest when you can to prevent overuse. 
• Try to avoid prolonged or repetitive shoulder movements, especially when your arm is above your head.
• Work on improving your posture. 
• Do exercises that strengthen your shoulder muscles and support the joints.
• Find a sleeping position that is comfortable and does not overstretch your arm or put it into an awkward position.
• Take steps to improve your overall health like eating a nutritious diet, getting regular physical activity, getting quality sleep, quitting smoking, and managing stress.

Summary

The four muscles that make up the rotator cuff are often referred to as SITS which stands for supraspinatus, infraspinatus, teres minor, and subscapularis. These muscles play important roles in the health and function of your shoulder. If one or more is injured, it can cause pain and trouble using your shoulder. 

If you hurt your rotator cuff, you may need shoulder rehab to heal from a rotator cuff injury and prevent future problems. There are also ways you can protect your shoulder muscles and keep them healthy to reduce your chances of hurting them.