The subscapularis muscle is unique among the rotator cuff muscles because it is located on which aspect of the scapula and inserts on which tubercle of the humerus?

Explanation

## Subscapularis: Unique Anatomical Position **Key Point:** Subscapularis is the only rotator cuff muscle located on the **anterior (costal) surface** of the scapula, making it anatomically and functionally distinct from the other three posterior rotator cuff muscles. ### Anatomical Features | Feature | Subscapularis | Other Rotator Cuff Muscles | |---------|---------------|---------------------------| | **Location** | Anterior (costal) surface of scapula | Posterior surface of scapula | | **Insertion** | Lesser tubercle of humerus | Greater tubercle (infraspinatus, teres minor); supraspinous fossa (supraspinatus) | | **Primary Action** | Internal rotation | External rotation (infraspinatus, teres minor); Abduction initiation (supraspinatus) | | **Innervation** | Upper and lower subscapular nerves | Suprascapular (supra/infra), Axillary (teres minor) | ### Clinical Significance - **Subscapularis tears** are less common than supraspinatus tears but are clinically significant - Loss of subscapularis → weakness in internal rotation and anterior instability - **Lift-off test** (Gerber's test) assesses subscapularis integrity: inability to lift hand off back indicates subscapularis dysfunction **High-Yield:** Subscapularis is the only anterior rotator cuff muscle — this anatomical uniqueness is frequently tested. **Clinical Pearl:** The subscapularis forms part of the anterior shoulder capsule and is crucial for preventing anterior humeral head dislocation.