The Rotator Cuff - S.I.T.S Muscles

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The rotator cuff is made up of four muscles. These individual muscles combine at the shoulder to form a thick "cuff" over this joint. The rotator cuff has the important job of stabilizing the shoulder as well as elevating and rotating the arm. Each muscle originates on the shoulder blade, or scapula, and inserts on the arm bone, or humerus.

The Four Rotator Cuff Muscles:

The four muscles that form the rotator cuff are the supraspinatus, infraspinatus, teres minor, and subscapularis.

Often the mnemonic S.I.T.S is used to help remember the muscles that make up the rotator cuff.

  • Supraspinatus: The supraspinatus muscle originates above the spine of the scapula and inserts on the greater tuberosity of the humerus. The supraspinatus abducts, or elevates, the shoulder joint out to the side. It also works with the other rotator cuff muscles to stabilize the head of the humerus in the glenohumeral joint, or shoulder joint.
  • 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 of the humerus. The infraspinatus externally rotates the shoulder joint. It also works with the other rotator cuff muscles to stabilize the head of the humerus in the glenohumeral joint, or shoulder joint.
  • 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 minor muscle externally rotates the shoulder joint. It also works with the other rotator cuff muscles to stabilize the head of the humerus in the glenohumeral joint, or shoulder joint.
  • Subscapularis: The subscapularis muscle originates on the anterior surface of the scapula, sitting directly over the ribs, and inserts on the lesser tuberosity of the humerus. The subscapularis muscle works to depress the head of the humerus allowing it to move freely in the glenohumeral joint during elevation of the arm. It also works with the other rotator cuff muscles to stabilize the head of the humerus in the glenohumeral joint, or shoulder joint.

    Al 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.

    What Can Go Wrong?

    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 tasks like lifting, reaching, or sleeping.

    Sometimes, shoulder pain can come on for no apparent reason. Wear and tear to 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 injured.

    Possible injuries and problems around your rotator cuff may include:

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

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

    Shoulder Pain: First Steps to Take

    When rotator cuff problems cause shoulder pain, you should consider visiting your doctor to have an examination and get an accurate diagnosis of your condition.

    You may benefit from the skilled services of a physical therapist 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. He or she 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 therapeutic exercises will likely be prescribed to help you restore normal mobility around your shoulder.

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

    Edited by Brett Sears, PT, About.com Physical Therapy Expert.

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