Origin

Infraspinous fossa of the scapula

Insertion

Middle facet of greater tubercle of the humerus

Action(s)

It is an external rotator of the glenohumeral joint and adductor of the arm.

The Infraspinatus and Teres minor rotate the head of the humerus outward (external rotation); they also assist in carrying the arm backward. Studies by Lastayo, w., etc. have shown the infraspinatus to be the major external rotator of the shoulder in comparison with the teres minor.

Nerve Supply

Suprascapular nerve

Arterial Supply

Suprascapular and circumflex scapular arteries

Physical Exam

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Clinical Importance

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Disease States

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Discussion

The tendon of this muscle is sometimes separated from the capsule of the shoulder-joint by a bursa, which may communicate with the joint cavity.

Figures

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Credits:

From Wikipedia:
Infraspinatus

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infraspinatus.png (image/png)