All of the following muscles form the rotator cuff EXCEPT:

Explanation

## Rotator Cuff Anatomy **Key Point:** The rotator cuff consists of four muscles that stabilize the glenohumeral joint and prevent humeral head subluxation during arm movement. ### The Four Rotator Cuff Muscles | Muscle | Origin | Insertion | Action | Innervation | | --- | --- | --- | --- | --- | | **Supraspinatus** | Supraspinous fossa | Greater tuberosity (superior facet) | Initiates abduction (0–15°) | Suprascapular nerve | | **Infraspinatus** | Infraspinous fossa | Greater tuberosity (middle facet) | External rotation | Suprascapular nerve | | **Subscapularis** | Subscapular fossa | Lesser tuberosity | Internal rotation | Upper and lower subscapular nerves | | **Teres minor** | Lateral border of scapula | Greater tuberosity (inferior facet) | External rotation | Axillary nerve | ### Why Teres Major Is NOT Part of the Rotator Cuff **Clinical Pearl:** Teres major is a **scapulohumeral muscle** (like latissimus dorsi) that assists in adduction and internal rotation, but it does NOT contribute to the dynamic stabilization function of the rotator cuff. It originates from the inferior angle of the scapula and inserts on the medial lip of the intertubercular groove. **High-Yield:** The mnemonic **"SITS"** helps recall the four rotator cuff muscles: **S**upraspinatus, **I**infraspinatus, **T**eres minor, **S**ubscapularis. Teres *major* is deliberately excluded. **Mnemonic:** **SITS** = Supraspinatus, Infraspinatus, Teres minor, Subscapularis (the true rotator cuff). ### Functional Significance The rotator cuff muscles work synergistically to: 1. Depress the humeral head (counteract superior migration by deltoid) 2. Stabilize the glenohumeral joint during arm elevation 3. Provide dynamic support during rotational movements Teres major, while important for shoulder movement, does not participate in this stabilization role and is therefore not classified as a rotator cuff muscle.