Subscapularis is a bulky triangular muscle, which fills the subscapular fossa.
Subscapularis originates from (a) medial 2/3rd of the costal surface of the scapula and (b) tendinous intermuscular septa connected to the ridges on the bone.
The fibres converge laterally into a broad tendon, which enters in front of the capsule of glenohumeral joint to be inserted on to the lesser tubercle of the humerus. The tendon is divided from the neck of the scapula by a large subscapular bursae, which usually interacts with all the synovial cavity of the shoulder joint.
The subscapularis is supplied by the upper and lower subscapular nerves (C5, C6).
Subscapularis is the medial rotator of the humerus. Along with supraspinatus, infraspinatus, and teres minor it stabilizes the head of the humerus in glenoid fossa during shoulder movements.
The origin, insertion, nerve supply, and actions of the scapulohumeral muscles are described in Table below: