The Anatomy of the Rotator Cuff

The four muscles that stabilize the shoulder and help move the arm

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Your rotator cuff in made up of four muscles that join together as tendons in your shoulder to form a thick covering at the top of the humerus (the bone in the upper arm). Each muscle originates on the shoulder ​blade (scapula) and connects to the humerus.

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

The Four Rotator Cuff Muscles
Verywell / Gary Ferster

Anatomy

There are four total muscles that form the rotator cuff:

  • 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, and 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.
  • 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.

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.

Function

Each rotator cuff muscle performs a specific and important function for your shoulder joint:

  • Stabilizing the head of the humerus in the shoulder joint: The supraspinatus, infraspinatus, teres minor, and subscapularis muscles all work together to achieve this.
  • Abducting or elevating the shoulder joint out to the side: These motions are performed by the supraspinatus.
  • Externally rotating the shoulder joint: The infraspinatus and teres minor muscles are responsible for this movement.
  • Depressing the head of the humerus: The subscapularis muscle performs this additional function to allow the humerus to move freely in the shoulder joint during the elevation of the arm.

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

Associated Conditions

Sometimes, shoulder pain can come on for no apparent reason. Wear and tear of the rotator cuff and shoulder joint may occur due to repetitive stress and postural neglect. When this happens, different structures around your rotator cuff may become compromised.

If you have suffered an injury to your rotator cuff, you may experience pain or weakness when lifting your arm. Your rotator cuff injury may cause difficulty with basic functional activities like lifting, reaching, or sleeping.

Possible injuries and problems with these four rotator cuff muscles may include:

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

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

Risk Factors for Rotator Cuff Injuries

There are certain motions and activities that increase your likelihood of suffering a rotator cuff injury. These include:

  • 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

Normal wear and tear of the rotator cuff, as well as aging, also increase the risk of injury. Accidents, such as a car accident or fall, can also result in a rotator cuff issue.

Working to maintain healthy joints, 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, prescribed treatment can range from simple rest and immobilization to surgery.

Because recovery from surgery to repair a torn rotator cuff can be slow, orthopedic surgeons tend to shy away from ordering these procedures with the exception of younger patients, those with major tears, or older patients whose jobs depend heavily on the shoulder function.

When rotator cuff problems cause shoulder pain, consider visiting your doctor to have an examination and get an accurate diagnosis of your condition. You may benefit from the services of a physical therapist (PT) to help figure out the cause of your shoulder pain and to work on restoring normal shoulder range of motion (ROM) and strength.

Your PT will ask you questions about your shoulder pain and problem. They may perform special tests for your shoulder to determine what structures are causing your pain and mobility issues.

Treatment for your rotator cuff may involve using therapeutic modalities to control the pain, and shoulder exercises will likely be prescribed to help you restore normal mobility of the joint. These exercises may include:

Your PT can teach you what to do now to treat your rotator cuff problem, and they should also show you how to prevent future problems with your SITS muscles.

You should consult a doctor before starting any rotator cuff exercise program. Stop any exercise that causes acute pain or discomfort in your shoulder.

A Word From Verywell

Knowing the four muscles of the rotator cuff and how they function is an important component to understanding your shoulder rehab. Check with your PT to learn more about your shoulder pain and the rotator cuff muscles that help support your shoulder.

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Article Sources
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  3. Mihata T, Morikura R, Hasegawa A, et al. Partial-thickness rotator cuff tear by itself does not cause shoulder pain or muscle weakness in baseball players. Am J Sports Med. 2019:47(14):3476-3482. doi:10.1177/0363546519878141

  4. American Academy of Orthopaedic Surgeons. Rotator cuff tears. Updated March 2017.

  5. Harvard Health Publishing. What to do about rotator cuff tendinitis. Updated May 19, 2019.