Muscle
Infraspinatus
Posterior cuff muscle for outward rotation
High-yield
Supraspinatus and infraspinatus share the suprascapular nerve. Infraspinatus works with teres minor in external rotation.
Overview
Below the scapular spine, infraspinatus pulls on the greater humeral tubercle to rotate the arm outward. With the other cuff muscles, it helps keep the humeral head centered during shoulder movement.
Learning this group? Read The rotator cuff muscles, explained.
Reference facts
- Origin
- Infraspinous fossa on the posterior scapula
- Insertion
- Middle facet of the humerus's greater tubercle
- Action
- Externally rotates the arm and supports glenohumeral stability
- Innervation
- Suprascapular nerve, mainly C5–C6
- Blood supply
- Branches of the suprascapular and circumflex scapular arteries
Clinical correlation
A cyst compressing the nerve at the spinoglenoid notch can weaken or waste infraspinatus while sparing supraspinatus, whose motor branches have already left the nerve. The visible weakness can vary because other muscles assist rotation.
Frequently asked questions
What does the infraspinatus do?
The infraspinatus externally rotates the arm and supports glenohumeral stability.
What nerve innervates the infraspinatus?
The infraspinatus is innervated by the suprascapular nerve, mainly C5–C6.
Where does the infraspinatus attach?
The infraspinatus originates from the infraspinous fossa on the posterior scapula and inserts on the middle facet of the humerus's greater tubercle.
What is the blood supply of the infraspinatus?
Branches of the suprascapular and circumflex scapular arteries.