|Insertion||Lesser tubercle of humerus|
|Action||Internal rotation of the shoulder
Stabilisation of glenohumeral joint
Can very weakly assist in shoulder adduction
|Nerve||Upper & lower branches of the subscapular neve (C5, C6, C7)|
Location & Overview
The subscapularis muscle is one of the shoulder’s four rotator cuff muscles. The remaining three rotator cuff muscles are: the supraspinatus, infraspinatus and teres minor. A useful way to remember the rotator cuff muscles is by using the acronym ‘SITS’ .
The subscapularis is the largest and strongest muscle of the rotator cuff. The subscapularis muscle is somewhat triangular in shape and the main bulk of the muscle fills the subscapular fossa (located on the anterior surface of the scapula). It gets its name from its location under the scapula: sub (under) scapula (wing bone). The subscapularis muscle and its tendons are the least likely to tear compared to the other rotator cuff muscles    .
Origin & Insertion
The subscapularis originates at the subscapular fossa of the scapula (specifically the medial and lower two-thirds of the groove on the lateral border) and inserts at the lesser tubercle of humerus (in front of the joint capsule). Some of the fibres also extend to the greater tubercle of the humerus and the bicipital groove. .
The primary action of the subscapularis is medial (internal) rotation. It is the only rotator cuff muscle able to perform medial rotation. In some positions, it can also assist very weakly in adduction of the humerus at the shoulder joint. The subscapularis also assists the other rotator cuff muscles in stabilization of the humerus in the glenohumeral joint   .
The upper subscapular nerve and lower subscapular nerve (C5, C6, C7) innervate the subscapularis muscle. This nerve originates from the posterior cord of the brachial plexus .
Blood is supplied to the subscapularis from the subscapular artery which is a branch of the axillary artery.
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|↑1, ↑6, ↑8, ↑11, ↑12||Maruvada S, Madrazo-Ibarra A, Varacallo M. Anatomy, Rotator Cuff. [Updated 2021 May 8]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK441844/|
|↑2||Aguirre K, Mudreac A, Kiel J. Anatomy, Shoulder and Upper Limb, Subscapularis Muscle. [Updated 2021 Aug 7]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK513344/|
|↑3||McCausland C, Sawyer E, Eovaldi BJ, Varacallo M. Anatomy, Shoulder and Upper Limb, Shoulder Muscles. 2021 Aug 13. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan–. PMID: 30521257.|
|↑4, ↑10||Kadi R, Milants A, Shahabpour M. Shoulder Anatomy and Normal Variants. J Belg Soc Radiol. 2017 Dec 16;101(Suppl 2):3. doi: 10.5334/jbr-btr.1467. PMID: 30498801; PMCID: PMC6251069.|
|↑5||Moore KL, Agur AMR, Dalley AF. Clinically Oriented Anatomy. 8th ed. Philadelphia: Lippincot Williams & Wilkins; 2017.|
|↑7, ↑9||Aguirre K, Mudreac A, Kiel J. Anatomy, Shoulder and Upper Limb, Subscapularis Muscle. [Updated 2021 Aug 7]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK513344/.|