Subscapularis Muscle: Action, Origin & Insertion

Instructor: Dan Washmuth

Dan has taught college Nutrition, Anatomy, Physiology, and Sports Nutrition courses and has a master's degree in Dietetics & Nutrition.

The subscapularis muscle is one of the most frequently used muscles of the shoulder joint. Educate yourself about the origin, insertion, and action of the subscapularis muscle by taking a look at this lesson.

The Wondrous Shoulder

The shoulder is one of the most amazing (and mobile) joints in the body. Compare your shoulder joint to your knee joint. Your knee can really only bend in one direction (if it bends in multiple directions you might need to see a doctor!). However, your shoulder can move your arm forward, backward, out to the side, and around in circles.

One of the reasons for the shoulder's great mobility is the subscapularis muscle. The subscapularis is a triangular-shaped muscle that is located on the inside surface of the scapula, which is commonly known as the shoulder blade. This muscle is the largest and strongest muscles of the rotator cuff, which is a collection of four muscles in the shoulder joint that functions to stabilize the shoulder.

Origin of the Subscapularis

The subscapularis originates from the subscapular fossa of the scapula. The subscapular fossa is the triangular-shaped, concave surface at the front of the scapula (the side of the scapula closest to the back of the rib cage).

The subscapularis muscle originates from the subscapular fossa, which is located on the front surface of the scapula.
subscapular fossa

Insertion Point of the Subscapularis

From the subscapular fossa, the subscapularis muscle extends out to the side of the body and inserts onto the humerus, which is the long bone of the upper arm. Specifically, this muscle inserts onto the lesser tubercle of the humerus. The lesser tubercle (also known as the lesser tuberosity) is a round prominence located at the front, top of the humerus. The lesser tubercle is located right next to the larger greater tubercle.

The subscapularis muscle inserts onto the round prominence at the front, top of the humerus called the lesser tubercle.
lesser tubercle

What Does the Subscapularis Do?

There are a couple of different actions of the subscapularis muscle. These actions include:

  • Medial rotation of the humerus: the inward turning or twisting of the upper arm, such as when you rotate your upper arm inward when you slam a door closed
  • Adduction of the humerus: moving the upper arm towards the body, such as the downward motion of your arms when you are flapping your arms
  • Stabilization of the shoulder joint: keeping the head of the humerus in its correct location against the scapula when the arm is moving throughout the shoulder joint

One of the actions of the subscapularis muscle is to adduct the arm.
adduction of the humerus

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