Pronator Quadratus Muscle – Anatomy, Nerve Supply

Last updated: February 8, 2026Reviewed date: February 8, 2026Reading time: 3 min read
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Pronator Quadratus Muscle is a square-shaped muscle on the distal forearm that acts to pronate (turn so the palm faces downwards) the hand. As it is on the anterior side of the arm, it is innervated by a branch of the median nerve, the anterior...

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Article Summary

Pronator Quadratus Muscle is a square-shaped muscle on the distal forearm that acts to pronate (turn so the palm faces downwards) the hand. As it is on the anterior side of the arm, it is innervated by a branch of the median nerve, the anterior interosseous nerve (roots C8 and T1 with T1 being primary). Arterial blood comes via the anterior interosseous artery. Structure of...

Key Takeaways

  • This article explains Structure of Pronator Quadratus Muscle in simple medical language.
  • This article explains Anatomy of Pronator Quadratus Muscle in simple medical language.
  • This article explains Origin and Insertion of Pronator Quadratus Muscle in simple medical language.
  • This article explains Nerve Supply of Pronator Quadratus Muscle in simple medical language.
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1

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2

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Pronator Quadratus Muscle is a square-shaped muscle on the distal forearm that acts to pronate (turn so the palm faces downwards) the hand. As it is on the anterior side of the arm, it is innervated by a branch of the median nerve, the anterior interosseous nerve (roots C8 and T1 with T1 being primary). Arterial blood comes via the anterior interosseous artery.

Structure of Pronator Quadratus Muscle

Its fibres run perpendicular to the direction of the arm, running from the most distal quarter of the anterior ulna to the distal quarter of the radius. It has two heads: the superficial head originates from the anterior distal aspect of the diaphysis (shaft) of the ulna and inserts into the anterior distal diaphysis of the radius, as well as its anterior metaphysis. The deep head has the same origin, but inserts proximal to the ulnar notch.[rx] It is the only muscle that attaches only to the ulna at one end and the radius at the other end.

Anatomy of Pronator Quadratus Muscle

Pronator quadratus
  • Origin: distal ulna
  • Insertion: distal radius
  • Action: pronation of the forearm
  • Innervation: median nerve

Origin and Insertion of Pronator Quadratus Muscle

Pronator quadratus is a flat, short, quadrilateral muscle that originates from the anterior surface of distal shaft of ulna and an aponeurosis that partially covers the muscle. Superficial muscle fibers project laterally and distally towards the anterior surface of distal shaft of radius, where they also insert. Deeper fibers insert superiorly to the ulnar notch of radius.

Nerve Supply of Pronator Quadratus Muscle

Pronator quadratus is innervated by the anterior interosseous nerve of forearm, with contributions mainly from C7 and C8 spinal nerves. The anterior interosseous nerve is a branch of the median nerve, which stems from the brachial plexus.

Blood supply

Pronator quadratus receives arterial blood from the anterior interosseous artery, which stems from the common interosseous artery. The latter is a branch of the ulnar artery.

Functions of Pronator Quadratus

Pronation of forearm (Pronatio antebrachii)
When pronator quadratus contracts, it pulls the lateral side of the radius towards the ulna, thus pronating the hand. Its deep fibers serve to keep the two bones in the forearm bound together. Moreover, this muscle can be absent in some humans, however, that does not affect the action of pronation very notably, as the pronator teres does the major role in that action.

Pronator quadratus produces forearm pronation by acting on the proximal radioulnar joint. During this movement, the head of radius pivots around the ulna, turning the palm posteriorly or inferiorly, if the forearm is flexed. This action of pronator quadratus is aided by the pronator teres and brachioradialis muscles.The location of this muscle across the distal forearm attributes it a protective role. When upward pressure is applied during weight-bearing activities, pronator quadratus holds together the distal ends of the radius and ulna, protecting and stabilizing the distal radioulnar joint. It also protects the interosseous membrane during forced and rapid forearm rotations by dissipating the forces pulling on the membrane.

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Tests to discuss with doctor
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Questions to ask
  • What is the most likely cause of my symptoms?
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Emergency warning signs such as chest pain, severe breathing difficulty, sudden weakness, confusion, severe dehydration, major injury, or loss of bladder/bowel control need urgent medical care. Do not wait for online information.

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Care roadmap for: Pronator Quadratus Muscle – Anatomy, Nerve Supply

Use this simple roadmap to understand the next safe steps. It is educational and does not replace examination by a doctor.

Go to emergency care if you notice:
  • Severe or rapidly worsening symptoms
  • Breathing difficulty, chest pain, fainting, confusion, severe weakness, major injury, or severe dehydration
Doctor / service to discuss: Qualified healthcare provider; specialist depends on symptoms and examination.
  1. Step 1

    Check danger signs first

    If danger signs are present, seek emergency care and do not wait for online information.

  2. Step 2

    Record the symptom story

    Write when symptoms started, severity, medicines already taken, allergies, pregnancy status, and test results.

  3. Step 3

    Visit a qualified clinician

    A doctor, nurse, or qualified healthcare provider can examine you and decide which tests or treatment are needed.

  4. Step 4

    Do only useful tests

    Do tests after clinical assessment. Avoid unnecessary tests, random antibiotics, or repeated medicines without diagnosis.

  5. Step 5

    Follow up and return early if worse

    If symptoms worsen, new warning signs appear, or treatment is not helping, return for review quickly.

Rural patient practical tips
  • Take a written symptom diary and all previous prescriptions/test reports.
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This roadmap is for education. A real diagnosis and treatment plan requires history, examination, and clinical judgment.

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Frequently Asked Questions

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When should I seek urgent care?

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