Infraspinatus & Teres Minor

Infraspinatus

Origin:  Infraspinous fossa (immediately below spine of scapula)

Insertion: Greater tuberosity of the humerus

Innervation: Suprascapular nerve (C4 - C6)

Action:  External rotation

Teres Minor

Origin: Lateral border of the scapula (lateral and inferior to infraspinatus origin)

Insertion: Greater tuberosity of the humerus

Innervation:  Axillary nerve (C5, C6)

Action:  External rotation and weak adduction

Why do I care:  These two external rotators are an integral part of the rotator cuff.  They have the best lever arm to externally rotate the shoulder, allowing the greater tuberosity to rotate away from the coracoid process of the scapula.  This ultimately allows us to reach or push objects over our heads without jamming our rotator cuff tendons between the greater tuberosity and acromion process.  Chronic computer and phone use can cause these muscles to become stretched out.  A stretched out muscle is a weak muscle in most cases.  To prevent this, make sure that you regularly stretch your pecs, subscapularis and anterior shoulders.