Pronator Quadratus
Forearm · Upper Limb
The pronator quadratus is a flat, square muscle spanning the distal forearm deep to the other flexors. It runs transversely from the distal anterior surface of the ulna to the distal anterior surface of the radius. It is the prime mover of pronation, initiating the movement before pronator teres assists, and it also helps bind the radius and ulna together to resist their separation. Its nerve supply is the anterior interosseous branch of the median nerve (C8, T1).
Origin, Insertion, Action & Nerve
Origin
Distal anterior surface of ulna
Insertion
Distal anterior surface of radius
Action
Pronation of forearm; holds radius and ulna together
Nerve
Anterior interosseous branch of median nerve (C8, T1)
Attachments explained
The Pronator Quadratus is defined first by where it attaches. Its origin is the more fixed anchor, usually the proximal or more stable end that stays put during contraction, while its insertion is the more mobile point that is pulled toward the origin when the muscle shortens.
Origin
Distal anterior surface of ulna
Insertion
Distal anterior surface of radius
Action & function
When the Pronator Quadratus contracts, it produces the following movements: Pronation of forearm; holds radius and ulna together.
As part of the Forearm group of the Upper Limb, it works alongside neighbouring muscles to generate smooth, coordinated movement and to stabilise the structures it acts on.
Nerve supply & clinical relevance
The Pronator Quadratus receives its nerve supply from the Anterior interosseous branch of median nerve (C8, T1). This nerve carries fibres from spinal segment(s) C8, T1.
Because a muscle can only contract when its nerve is intact, injury to the Anterior interosseous branch of median nerve or to its spinal roots (C8, T1) can weaken or paralyse the Pronator Quadratus, impairing the movements it normally produces (pronation of forearm). This is why knowing the innervation is central to localising nerve lesions in clinical practice.
How to study the Pronator Quadratus (the OIANS method)
Picture pronator quadratus as a square patch bridging the two forearm bones near the wrist. Its transverse fibres pulling the radius across the ulna make it the prime initiator of pronation, with pronator teres joining in when more power is needed. Learning the two pronators as a deep-and-superficial pair keeps them organised.
Add its second job, binding the distal radius and ulna together, and its nerve, the anterior interosseous branch of the median nerve shared with the deep thumb and finger flexors. That grouping ties this small muscle to the rest of the deep flexor layer.
Frequently asked questions
Where is the Pronator Quadratus located?
The Pronator Quadratus is a muscle of the Forearm group, located in the Upper Limb.
What is the origin of the Pronator Quadratus?
Distal anterior surface of ulna
What is the insertion of the Pronator Quadratus?
Distal anterior surface of radius
What movements does the Pronator Quadratus produce?
Pronation of forearm; holds radius and ulna together
What nerve supplies the Pronator Quadratus?
Anterior interosseous branch of median nerve (C8, T1)
Is the Pronator Quadratus free to study in OIANS?
Yes. The Pronator Quadratus is free in OIANS: its full origin, insertion, action and nerve details are open to everyone in the Muscle Directory, and because it belongs to the Upper Limb it is also covered by the free Quiz and Flashcard decks. The other regions, the "All Muscles" deck, and the Progress and Explore tools are unlocked with a one-time Lifetime purchase.
Related muscles
Study the Pronator Quadratus
Test yourself on Upper Limb muscles with interactive quizzes and flashcards in the free OIANS app.
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