The rotator cuff is composed of four muscles. Which of the following is NOT a rotator cuff muscle?

Question

Accepted Answer

A. Teres major. ## Rotator Cuff Composition: The Four Muscles

**Key Point:** The rotator cuff consists of exactly four muscles: supraspinatus, infraspinatus, teres minor, and subscapularis. Teres major is NOT part of the rotator cuff—it is a separate muscle of the shoulder girdle.

**Mnemonic:** **SITS** = Supraspinatus, Infraspinatus, Teres minor, Subscapularis (the four rotator cuff muscles)

### The Four Rotator Cuff Muscles

| Muscle | Origin | Insertion | Action | Innervation |
|--------|--------|-----------|--------|-------------|
| Supraspinatus | Supraspinous fossa | Superior facet of greater tubercle | Abduction (0–15°) | Suprascapular nerve |
| Infraspinatus | Infraspinous fossa | Middle facet of greater tubercle | External rotation | Suprascapular nerve |
| Teres minor | Lateral border of scapula | Inferior facet of greater tubercle | External rotation | Axillary nerve |
| Subscapularis | Subscapular fossa | Lesser tubercle | Internal rotation | Upper/lower subscapular nerves |

### Why Teres Major Is NOT in the Rotator Cuff

**High-Yield:** Teres major is a separate muscle that:
- **Origin:** Inferior angle and lower lateral border of scapula
- **Insertion:** Medial lip of intertubercular groove of humerus
- **Action:** Internal rotation, adduction, extension (assists latissimus dorsi)
- **Innervation:** Lower subscapular nerve
- **Function:** Part of the "lat-teres major" complex for powerful internal rotation and shoulder extension, NOT rotator cuff stabilization

**Clinical Pearl:** Teres major is sometimes called a "helper" muscle to the rotator cuff but is NOT functionally or anatomically part of it. The rotator cuff's primary role is dynamic stabilization of the glenohumeral joint; teres major is a mover muscle.

![Rotator Cuff and Shoulder Joint diagram](https://mmcphlazjonnzmdysowq.supabase.co/storage/v1/object/public/blog-images/explanation/4291.webp)

Answer

B. Subscapularis

Answer

C. Infraspinatus

Answer

D. Supraspinatus

The rotator cuff is composed of four muscles. Which of the following is NOT a rotator cuff muscle?

Explanation

Rotator Cuff Composition: The Four Muscles

The Four Rotator Cuff Muscles

Why Teres Major Is NOT in the Rotator Cuff

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Muscle	Origin	Insertion	Action	Innervation
Supraspinatus	Supraspinous fossa	Superior facet of greater tubercle	Abduction (0–15°)	Suprascapular nerve
Infraspinatus	Infraspinous fossa	Middle facet of greater tubercle	External rotation	Suprascapular nerve
Teres minor	Lateral border of scapula	Inferior facet of greater tubercle	External rotation	Axillary nerve
Subscapularis	Subscapular fossa	Lesser tubercle	Internal rotation	Upper/lower subscapular nerves