The infraspinatus muscle is a deep muscle of the posterior thoracic wall. Its proximal attachment (origin) is the infraspinous process (of the scapula). The distal attachment (insertion) is the greater tubercle of the humerus. The innervation is the suprascapular nerve and the main function of the muscle is to laterally rotate the arm (i.e., to turn the hand and the thumb in a clockwise rotation.
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