The subscapular muscle is a flat extensive muscle which occupies the subscapular fossa, beyond which it extends cranially and caudally. It arises form the fossa, crosses the shoulder joint on the medial aspect and inserts, deep to the coracobrachial muscle, on the lesser tubercle of the humerus. It is divided into several portions by tendinous bands. It functions as a medial collateral ligament of the shoulder joint.
Origin: Subscapular fossa.
Insertion: Lesser tubercle of the humerus.
Action: Primarily to adduct and extend the shoulder joint and to draw the humerus forward, during flexion of the joint, it aids in maintaining flexion.