Subscapularis

Introduction

Introduction to Subscapularis Muscle

The subscapularis is one of the four rotator cuff muscles, located on the anterior (deep) surface of the scapula. It forms part of the posterior scapular region but acts on the glenohumeral joint. In the scapular-deltoid region, it lies deep to the deltoid and is separated from the scapula by the subscapular bursa.

Study

Origin, Insertion, Action & Innervation

Origin: Subscapular fossa (medial two-thirds of the anterior surface of the scapula). Insertion: Lesser tubercle of the humerus. Action: Medial rotation and adduction of the glenohumeral joint; stabilizes the humeral head against the glenoid (anterior stabilizer). Innervation: Upper and lower subscapular nerves (C5-C6, from posterior cord of brachial plexus). Blood supply: Subscapular artery (branch of axillary artery) and suprascapular artery.

Clinical Relevance

Subscapularis tears are less common than supraspinatus tears but can occur with anterior shoulder dislocation or repetitive overhead activity. The 'lift-off test' and 'belly-press test' assess subscapularis function. The subscapular bursa reduces friction between the muscle and scapular neck.

Summary

Key Takeaways – Subscapularis

1. Only rotator cuff muscle on the anterior scapula. 2. Primary internal rotator of the shoulder. 3. Innervated by upper & lower subscapular nerves (C5-C6). 4. Tested clinically with lift-off/belly-press maneuvers. 5. Important anterior stabilizer of the glenohumeral joint.