What is the Subscapularis Muscle?

The subscapularis muscle is the triangular-shaped muscle that fills the subscapular fossa and inserts into the smaller tubercle of the humerus. From there, the large subscapularis muscle attaches to the front shoulder joint. Injury of this muscle is common, particularly among athletes.

The scapula is more commonly known as the shoulder blade. The scapula is the bone that connects the humerus, or arm bone, to the clavicle, also known as the collar bone. The subscapularis muscle begins at the lower portion of the scapula and ends at a tendon inserted into the humerus. The muscle then extends to the front of the shoulder joint.

The scapula separates the subscapularis muscle tendon from the scapula with a large bursa, a small sac that is filled with fluid. The bursa acts as a cushion between muscles and joints or between bones and tendons.

The primary role of the subscapularis muscle is to aid in movement of the shoulder. When in the arm is raised, this muscle moves the humerus downward and forward simultaneously. This acts as a defense mechanism, helping to protect the shoulder joint itself. It also helps the keep the humerus from becoming displaced.

The subscapularis muscle is part of the group of rotator cuff muscles. Athletes are particularly vulnerable to injuries involving this group of muscles. Injury is most common among athletes who throw a lot, such as baseball players. A partial rupture of the subscapularis muscle is the most common injury, although complete ruptures do sometimes occur.

Common symptoms of a subscapularis muscle injury include shoulder pain upon movement, particularly when the arms are raised above the head. Rotating the arm inward also tends to cause pain and discomfort with this type of injury. Pressing against the area where the tendon inserts itself often causes intense pain as well.

In the case of a partial rupture of the subscapularis muscle, resting the muscle is vital. Without proper rest, healing will be delayed, causing the injury to require more healing time, perhaps several months as opposed to the several weeks it normally takes. A doctor specializing in sports medicine can assist the patient with healing techniques specific to the individual's particular injury.

In the event of a complete rupture of the subscapularis muscle or the corresponding tendon, surgery is often required. Medical assistance is vital in this instance. If the rupture is not treated in a timely fashion, it is possible to incur some degree of permanent injury.