Rotator Cuff Muscles (SITS)
The rotator cuff is a group of four muscles that act as a dynamic stabilizer of the glenohumeral joint. They originate on the scapula and insert on the greater or lesser tubercles of the humerus.
| Muscle | Primary Action | Innervation |
|---|---|---|
| Supraspinatus | Abduction (first 15°) | Suprascapular nerve |
| Infraspinatus | Lateral (external) rotation | Suprascapular nerve |
| Teres Minor | Lateral (external) rotation / Adduction | Axillary nerve |
| Subscapularis | Medial (internal) rotation / Adduction | Upper/Lower subscapular nerve |
High-Yield Clinical Notes:
- Mnemonic: SITS (Supraspinatus, Infraspinatus, Teres minor, Subscapularis).
- Most Common Injury: The supraspinatus tendon is the most frequently injured due to its location under the acromion, where it is prone to impingement.
- Empty Can Test: Used to assess the supraspinatus muscle for tear or tendinopathy.
- Insertion Note: All except the subscapularis insert on the greater tubercle; the subscapularis inserts on the lesser tubercle.