The rotator cuff muscles originate from the scapula and insert on the proximal humerus. Which muscle is the exception, originating from the anterior surface of the scapula rather than the posterior or lateral borders?

Explanation

## Subscapularis: The Anterior Rotator Cuff Muscle **Key Point:** The subscapularis is the only rotator cuff muscle that originates from the anterior (costal) surface of the scapula. All other rotator cuff muscles originate from the posterior surface of the scapula. **High-Yield:** Subscapularis is the largest and strongest of the rotator cuff muscles. It lies deep to the serratus anterior and occupies the subscapular fossa on the anterior scapula. **Mnemonic:** **SITS** = Supraspinatus, Infraspinatus, Teres minor, Subscapularis — but remember that three of these (S, I, T) are posterior, while the fourth (S) is anterior. ### Anatomical Origins of Rotator Cuff | Muscle | Origin | Surface | Insertion | |--------|--------|---------|----------| | Subscapularis | Subscapular fossa | **Anterior** scapula | Lesser tubercle of humerus | | Supraspinatus | Supraspinous fossa | Posterior scapula | Greater tubercle (superior facet) | | Infraspinatus | Infraspinous fossa | Posterior scapula | Greater tubercle (middle facet) | | Teres minor | Lateral border | Posterior scapula | Greater tubercle (inferior facet) | **Clinical Pearl:** Subscapularis is the primary internal rotator of the shoulder. Injury to this muscle results in loss of internal rotation strength and is often missed on standard rotator cuff assessment because the "lift-off test" (Gerber's test) is required to isolate it.