Musculus subscapularis
The subscapularis is a large, powerful muscle filling the subscapular fossa on the medial surface of the scapula. It originates from the entire medial surface of the scapula and inserts on the lesser tubercle (medial tuberosity) of the humerus. Its actions are to medially rotate and adduct the humerus and stabilize the shoulder medially. It is innervated by the subscapular nerves (roughly C6-C7). It is the primary medial stabilizer of the shoulder joint, preventing lateral luxation.
Origin: Subscapular fossa (entire medial surface of the scapula)
Insertion: Lesser tubercle (medial tuberosity) of the humerus
Action: Medially rotates and adducts the humerus; stabilizes the shoulder medially
Innervation: Subscapular nerves (C6-C7)
Isolated injury is uncommon. Relevant in evaluations of shoulder stability and after trauma. Dysfunction can contribute to shoulder instability.
## Overview Strain of the subscapularis compromises medial shoulder stability and can allow the shoulder to pop laterally. It is seen in horses that slip or splay. Signs include shoulder instability,
Sudden shoulder instability or swelling after trauma should be evaluated.
## Overview Strain of the subscapularis compromises medial shoulder stability and can allow the shoulder to pop laterally. It is seen in horses that slip or splay. Signs include shoulder instability, lateral clicking, forelimb lameness worse on uneven ground, and axillary swelling. ## Causes Acute abduction or trauma. ## Diagnosis Palpation, gait evaluation, and ultrasound. ## Treatment Rest and rehabilitation. Severe instability may need surgical stabilization. ## Recovery and Prognosis Fair to good for strains. More guarded if frank subluxation occurs. ## Prevention Safe footing. Signs include: shoulder joint instability; lateral popping or clicking; forelimb lameness worse on uneven ground; axillary swelling
Isolated injury is uncommon. Relevant in evaluations of shoulder stability and after trauma. Dysfunction can contribute to shoulder instability.
Sudden shoulder instability or swelling after trauma should be evaluated.
See the Subscapularis on our interactive 3D horse model. Open 3D Model