The subscapularis muscle is an important muscle of the shoulder. It is one of four muscles that comprise the rotator cuff. The subscapularis plays a role in maintaining shoulder function and movement.
Understanding the Subscapularis
The subscapularis is a large, triangular muscle located on the anterior surface of the scapula, or shoulder blade. It originates from the medial two-thirds of the subscapular fossa, a depression on the front of the shoulder blade. Its fibers form a tendon that crosses the shoulder joint and inserts onto the lesser tubercle of the humerus, a bony prominence on the front of the upper arm bone, and into the anterior part of the shoulder joint capsule. It is the largest and strongest of the four rotator cuff muscles.
Key Actions of the Subscapularis
The primary action of the subscapularis muscle is the internal, or medial, rotation of the humerus. This involves rotating the upper arm inward towards the body’s midline, such as when reaching across the chest. It is the only rotator cuff muscle with this primary function.
The subscapularis also contributes to the adduction of the humerus, bringing the arm closer to the side of the body. These actions are seen in daily activities and athletic endeavors, such as the winding motion before a tennis serve, arm swing during walking, or reaching behind one’s back. Its superior fibers can assist with abduction, while inferior fibers aid in adduction.
The Subscapularis and Shoulder Stability
The subscapularis muscle contributes to the stability of the glenohumeral joint, the ball-and-socket joint of the shoulder. It helps keep the head of the humerus centered within the shallow glenoid fossa, the socket of the shoulder blade. This centering action prevents dislocations and ensures smooth movement throughout the shoulder’s range of motion.
The muscle contributes to “concavity compression,” compressing the humeral head into the glenoid fossa to enhance joint stability. As part of the rotator cuff, the subscapularis works with the supraspinatus, infraspinatus, and teres minor muscles. This collective effort provides dynamic anterior support to the glenohumeral joint.
Maintaining Subscapularis Health
Maintaining subscapularis health involves a general approach to shoulder care. Proper posture helps align the shoulder joint, reducing stress on the muscle. Balanced exercise routines targeting the entire shoulder complex are beneficial.
These routines should include strengthening exercises and gentle stretching to promote muscle flexibility and reduce soreness. Avoid activities that cause pain or discomfort, as repetitive stress can lead to issues. Incorporating cross-training can help prevent overuse injuries by varying demands on the shoulder.