Rotator Cuff Muscles Origin Insertion and Action
The rotator cuff comprises four muscles — SITS (Supraspinatus, Infraspinatus, Teres minor, Subscapularis) — that stabilize the glenohumeral joint and enable shoulder rotation. Mastering their origins, insertions, and actions is essential for USMLE Step 1, anatomy practicals, and orthopedic clinical reasoning. Each card covers a muscle's bony attachments and primary movement to help you ace rotator cuff questions.
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5 CardsWhat nerve innervates supraspinatus?
SITS mnemonic — what does it stand for?
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What is the most commonly torn rotator cuff muscle?
Supraspinatus is the most commonly torn rotator cuff muscle due to its position under the acromion and coracoacromial ligament. It is frequently damaged during repetitive overhead activity or a fall on an outstretched hand.
- Presents with painful arc (60°–120°)
- Positive empty-can test
How do I remember the rotator cuff muscles?
Use the SITS mnemonic: Supraspinatus, Infraspinatus, Teres minor, Subscapularis.
A helpful tip: the three external rotators (Supraspinatus, Infraspinatus, Teres minor) attach to the greater tubercle; Subscapularis (the internal rotator) attaches to the lesser tubercle.
What is the difference between teres minor and teres major?
Teres minor is a rotator cuff muscle innervated by the axillary nerve; it externally rotates the humerus. Teres major is NOT part of the rotator cuff, is innervated by the lower subscapular nerve, and internally rotates and adducts the arm.
- Teres minor → rotator cuff, external rotation
- Teres major → not rotator cuff, internal rotation