Pronator Quadratus: a forearm pronator

 PRONATOR QUADRATUS!

Pronator: hinting that it can perform the muscle action of pronation.
Quadratus: referring to its 4 corners / square-like shape

Pronator Quadratus lives deep in your wrist -underneath the cord-like tendons of the wrist flexor muscles. It attaches itself to the ends of both forearm bones on the inside of the wrist - so it's actually the deepest on the anterior side

I like to think of this muscle as the lil' sister of last week's larger pronator - Pronator Teres 

 Attachment points:

Origin: Distal 1/4 of the anterior shaft of the ulna

Insertion:  Distal 1/4 of the anterior shaft of the radius

see bony landmarks at end of this post :)

 Muscle Actions:

pronation of the forearm at the radio-ulnar joint

Pronation of the forearm is the act of flipping your hand from palm up to palm down.  This turning actually action happens at the radio-ulnar joint, which is located just below the elbow


*As I hinted above, this muscle helps out with pronation, leaving most of the work to big sister Pronator Teres




We'll end with some bony landmarks !

Pronator Teres: a forearm pronator

We're still in the forearm but we're moving away from the wrist flexor group and heading into pronator town! Meet PRONATOR TERES:

 Lives on the anterior (front) surface of your forearm - just below the elbow !
Visually to me, Pronator Teres looks like a 'sash' ribbons one would wear if perhaps they were a ..."pro" at something ? ;) that's how I remember anyway!

 Pronator Teres Muscle Attachment Points:

Origin(s): (two heads)

a) Humeral Head:  medial supracondylar ridge and the medial epicondyle of the humerus

b) Ulnar head:  Coranoid process of the Ulna

aka: just above & below the elbow on the inside > then in crosses over to...

Insertion:  middle 1/3 of the lateral radius (that forearm bone on the 'thumb-side' of the forearm)
(it actually inserts right next to where your bicep muscle inserts!)

 Pronator Teres Muscle Actions:

a) pronation of the forearm at the radio ulnar joint  (see below*)

b) flexion of the forearm at the elbow joint (arm bending in half)

*Pronation is act of flipping your hand from facing UP (supinate/supination)
to facing DOWN (to pronate/pronation)

Another common association to remember the muscle action pronation/supination is that when you're holding a bowl of soup you must supinate your forearm/hand but if you pronate..you are 'prone to spill it' ! Get it?