Subscapularis

The subscapularis muscle, one of the four rotator cuff muscles, plays a crucial role in shoulder stability and internal rotation. For athletes—especially those involved in overhead or throwing sports like baseball, tennis, or swimming—the subscapularis is essential for generating force and maintaining proper joint mechanics.

Weakness or dysfunction in this muscle can compromise performance and increase the risk of shoulder injuries, making it a key focus in both training and rehabilitation programs.

Subscapularis
Subscapularis

Subscapularis

Anatomy

[Origin]

  • Subscapular fossa (most of anterior surface of scapula)

[Insertion]

  • Lesser tubercle of humerus

    [Action]

    • Medially rotates arm; as part of rotator cuff, helps hold head of humerus in glenoid cavity
    • It helps in shoulder adduction and extension in certain positions.

    Clinical Relevance

    It is often injured by throwers. Tenderness and pain will be felt when pressing in on the tendon insertion on the inside of the upper arm. Subscapularis tendonitis symptoms include pain when moving the shoulder especially when the arm is raised above the shoulders.

    An overworked subscapularis muscle may make you feel like you are not able to lift your arm. It may be even responsible for your frozen shoulder.

    ~ Evidence-Based Exercises ~

    According to an EMG study, the exercises that demonstrated significant muscle contractions of Subscapularis are;

      • Shoulder Internal Rotation
      • 90/90 Internal Rotation
      • Lift-Off Test

    Shoulder IR

    Shoulder IR

    90/90 IR

    Shoulder IR

    Lift-Off

    Lift Off

    < Reference >