infraspinatus

Introduction

Intrinsic muscle of the shoulder (scapulohumeral). One of its tendons contributes to formation of the "rotator cuff".

Origin

infraspinous fossa of the scapula

Insertion

• middle facet of the greater tubercle of humerus

Action

• extends arm
• rotates arm laterally
• tonic contraction helps to hold the head of the humerus in the shallow glenoid fossa

Innervation

• suprascapular nerve (C5, C6)

More general terms

• skeletal muscle (voluntary muscle)