Infraspinatus
Shoulder & Arm
If you can't comb your hair or reach behind your head, this muscle might be the problem.
Function
Externally rotates arm, stabilizes glenohumeral joint
Origin
Infraspinous fossa of scapula
Insertion
Greater tubercle of humerus (middle facet)
Innervation
Suprascapular nerve (C5-C6)