Corpus: Subscapular muscle

Origin

The origin of the subscapular muscle is located at the subscapular fossa on the ventral side of the scapula and completely fills it.

Insertion

The insertion of the subscapular muscle is at the lesser tubercle of the humerus. Some of its tendon fibers radiate into the capsule of the shoulder joint.

The innervation of the subscapular muscle is provided by the subscapular nerves, short motor branches from the posterior fasciculus of the brachial plexus (segments: C5-C7).

The subscapular muscle is the most important muscle for the internal rotation of the upper arm and contributes to adduction with the arm raised. An additional function of the subscapular muscle is the tensioning of the relatively loose capsule of the shoulder joint.

• Paralysis: In the case of paralysis of the subscapular muscle, there is an external rotation position of the limb, indicating its critical function as an internal rotator.

• Trauma: A rare subtype of rotator cuff tear is the subscapular tendon rupture (SSC rupture).

Diagnostically, the function of the subscapular muscle can be tested using the Lift-Off Test (“Gerber’s test”) and the Belly-Press Test ("Napoleon Test").