Subjects and lessons to explore.

Law

Clinical Mnemonics · Anatomy & Musculoskeletal

SITS (Rotator Cuff)

4 min read
4 key termsReport an error
Want it in plain words first? Jump to Eli explains — the same idea, no jargon.
On this page 4 sections
  1. In 30 seconds
  2. The college version
  3. Eli explains
  4. Study tools

In 30 seconds

Names the four rotator-cuff muscles - Supraspinatus, Infraspinatus, Teres minor, Subscapularis - that stabilize and move the shoulder.

The college version

Names the four rotator-cuff muscles - Supraspinatus, Infraspinatus, Teres minor, Subscapularis - that stabilize and move the shoulder.

S — Supraspinatus

Supraspinous fossa (above the scapular spine) to superior facet of greater tubercle; initiates abduction (first ~15 degrees)

Initiates abduction (first ~15 degrees) before the deltoid becomes effective. Innervated by the suprascapular nerve (C5-C6). Passes beneath the acromion and is the most commonly torn rotator-cuff tendon; associated with subacromial impingement and a painful arc (60-120 degrees).

Physiology. Sits at a mechanically favorable angle to begin abduction; the deltoid's line of pull is poor when the arm hangs at the side.

Safety. A large supraspinatus tear combined with other cuff tears can cause profound weakness; early recognition and referral prevent a chronically weak shoulder.

I — Infraspinatus

Infraspinous fossa (below the scapular spine) to middle facet of greater tubercle; external rotation

Primary external (lateral) rotator of the arm. Innervated by the suprascapular nerve (C5-C6). Frequently torn alongside the supraspinatus in posterosuperior cuff tears.

Physiology. External rotation lets you turn the forearm out (reaching behind the back, pitching); the infraspinatus is the main engine for that motion.

Safety. Posterior shoulder pain with external-rotation weakness in throwing athletes warrants evaluation for a cuff tear.

T — Teres minor

Lateral (axillary) border of scapula to inferior facet of greater tubercle; external rotation + stabilization; axillary nerve

Assists external rotation and adduction and stabilizes the humeral head in the glenoid. Innervated by the axillary nerve (C5-C6) - the only cuff muscle it supplies; the axillary nerve also innervates the deltoid.

Physiology. Acts as a dynamic stabilizer of the shallow glenohumeral joint, like a seatbelt keeping the ball on the tee.

Safety. Do not confuse with teres major (internal rotation/adduction, lower subscapular nerve). Axillary-nerve injury weakens both teres minor and deltoid.

S — Subscapularis

Subscapular fossa (anterior scapula) to lesser tubercle; internal rotation; subscapular nerves

Primary internal (medial) rotator and the largest, strongest cuff muscle; the only cuff muscle inserting on the lesser tubercle. Innervated by the upper and lower subscapular nerves (C5-C7). Assessed with the lift-off and belly-press tests.

Physiology. Resists anterior translation of the humeral head (a front 'seatbelt'), reducing anterior dislocation risk.

Safety. Positive lift-off or belly-press test indicates subscapularis dysfunction; evaluate after anterior dislocation.

Memory aids

  • S = Supraspinatus
  • I = Infraspinatus
  • T = Teres minor
  • S = Subscapularis

Quick review

  • S = Supraspinatus — Supraspinous fossa (above the scapular spine) to superior facet of greater tubercle; initiates abduction (first ~15 degrees)
  • I = Infraspinatus — Infraspinous fossa (below the scapular spine) to middle facet of greater tubercle; external rotation
  • T = Teres minor — Lateral (axillary) border of scapula to inferior facet of greater tubercle; external rotation + stabilization; axillary nerve
  • S = Subscapularis — Subscapular fossa (anterior scapula) to lesser tubercle; internal rotation; subscapular nerves
Eli, the EliExplains learning guide

Eli explains

The same idea, in plain words

Explain it like I’m 10

A real word made from the first letters of the four muscles that wrap around your shoulder like a cuff, holding the ball of your arm bone in its shallow cup.

S — Supraspinatus. The 'starter motor' muscle above the shelf on your shoulder blade. It gets your arm moving out to the side for the first little bit before the big deltoid takes over, and because it runs through a tight gap under the shoulder roof, it's the muscle that gets pinched and torn most often.

I — Infraspinatus. The 'turn-out' muscle below the shelf on your shoulder blade. It rotates your arm outward like you're unscrewing a jar, and it shares its nerve with the supraspinatus, so the two often get torn together.

T — Teres minor. A thin muscle along the outer edge of your shoulder blade, near the armpit. It helps turn the arm outward and acts like a little seatbelt holding the shoulder ball in its socket. It's famous for being the only cuff muscle powered by a different nerve - the axillary nerve.

S — Subscapularis. The big 'turn-in' muscle on the front of your shoulder blade, between the blade and your ribs. It rotates your arm inward like turning a doorknob, and it's the biggest, strongest of the four - the only one sitting on the front instead of the back.

Keep learning

Ready to build on this? Continue to the next lesson.

Study tools & related lessonsKey vocabulary · Related

Key vocabulary

S
Supraspinatus
I
Infraspinatus
T
Teres minor
S
Subscapularis

Educational content only. It is not medical, legal or professional advice. Found an error? Tell us.