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Pronator Teres Muscle Anatomy

Quick Overview View Flashcards
Origin
  • Humeral head: Medial supracondylar ridge of the humerus
  • Ulnar head: Coronoid process of the ulna
Insertion
  • Lateral mid-shaft of the radius
Action
  • Pronation of the forearm
  • Contributes to flexion of the forearm at the elbow
Innervation
  • Median nerve (C6-C7)
Blood Supply
  • Branches of the brachial, radial, and ulnar arteries
Last updated: Estimated Reading Time: 6 min

Location & Overview

The pronator teres muscle is a forearm muscle with both humeral and ulnar heads. It is located laterally in the most superficial layer of the anterior muscles of the forearm. The distal anterior surface of the pronator teres is covered by the brachioradialis muscle.[1,2] The pronator teres muscle gets its name due to its shape and action. ‘Pronator’ refers to its action of pronation, and ‘teres’ refers to its long, rounded shape.[3] Images of the pronator teres are included further down the page.

The median nerve typically passes through the humeral and ulnar heads of the pronator teres muscle. Compression of the median nerve is referred to as ‘pronator teres syndrome.’ However, variations in this arrangement exist, such as the median nerve passing through the muscle belly of the ulnar head of the pronator teres or being situated posteriorly to both muscle heads. In some individuals, the ulnar head of the pronator teres muscle is entirely absent (around 14% of people, according to research by Caetano et al. [2017]), while in others, the ulnar head is underdeveloped, with only a fibrous band originating from the ulna’s coronoid process (present in approximately 17% of individuals studied by Caetano et al. [2017]).[4] Although the absence of the ulnar head is rare, when it is missing, the likelihood of median nerve entrapment may be reduced.[3]

Irritation of the median nerve due to pronator teres syndrome can result from repetitive or rapid grasping and pronation movements. Activities such as tennis, hammering, rowing, and excessive exercise volume involving these movements by bodybuilders can contribute to median nerve entrapment and pronator teres syndrome. However, pronator teres syndrome is relatively rare, which may sometimes lead to misdiagnosis or confusion with more common conditions, such as carpal tunnel syndrome.[3]

pronator teres anterior view
Here, we can see the pronator teres from an anterior view.
pronator teres medial view
Here, we can see the pronator teres from a medial view. This allows us to see the two heads of origin: the larger humeral head and the smaller ulnar head.
pronator teres highlighted in red anterior view
Here, we can see the pronator teres highlighted in red from an anterior view, among the other muscles of the arm. You can see that the brachioradialis muscle covers the distal part of the pronator teres.
pronator teres highlighted in red medial view
Here, we can see the pronator teres highlighted in red from a medial view, among the other muscles of the arm. You can see the brachioradialis muscle covering the distal part of the pronator teres.

Origin & Insertion

The humeral head, the larger of the two heads, originates from the medial supracondylar ridge of the humerus. The smaller ulnar head originates from the coronoid process of the ulna. As the two heads travel down the forearm, they converge to form a common flexor tendon. This tendon then inserts into the middle of the shaft of the radius.[3,4,2]

pronator teres origin
Highlighted in red, we can see the origin of the pronator teres muscle. The humeral head’s origin is on the medial supracondylar ridge of the humerus, whereas the ulnar head originates on the coronoid process of the ulna.
insertion of the pronator teres
Highlighted in blue, we can see the insertion of the pronator teres on the lateral mid-shaft of the radius.

Action & Function

The pronator teres performs pronation of the forearm as its main action. It is also able to assist other muscles with flexion of the forearm at the elbow joint.[3,5,1]

These actions are beneficial in sports such as tennis, where forearm rotation is required for various strokes, such as backhands and forehands. In baseball, the pronator teres aids in rotating the forearm during throwing and when swinging the bat. Additionally, it contributes to forearm rotation during a golf swing. In everyday life, the pronator teres is useful for activities such as turning a doorknob or opening a jar, as it helps rotate the forearm to twist the doorknob or lid.

Image of a person demonstrating the movement of pronation of the hand.
This image demonstrates pronation, where the hand and forearm are rotated so that the back of the hand faces the front of the body while in the anatomical position. The opposite of pronation is supination. Pronation is the primary action of the pronator teres muscle.
Image of a person demonstrating the movement of elbow flexion.
This image demonstrates elbow flexion, which involves bending the elbow. The opposite movement of elbow flexion is elbow extension. Assisting other muscles with elbow flexion is a secondary action of the pronator teres.

Innervation

The median nerve innervates both heads of the pronator teres muscle from the C6 to C7 roots. The median nerve is a part of the brachial plexus.[3,1]

median nerve
Pictured here, we can see the median nerve, which innervates the pronator teres. The specific nerve roots that innervate the pronator teres are C6 and C7.
brachial plexus
Pictured here, we can see the brachial plexus. As shown in the image, the median nerve is a branch of the brachial plexus.

Blood Supply

Blood is supplied to the pronator teres muscle via the brachial, radial, and ulnar arteries.[6,1]

References

  1. [1] Olewnik Ł, Podgórski M, Polguj M, Wysiadecki G, Topol M. Anatomical variations of the pronator teres muscle in a Central European population and its clinical significance. Anat Sci Int. 2018;93(2):299-306. doi:10.1007/s12565-017-0413-y
  2. [2] Moore KL, Agur AMR, Dalley AF. Clinically Oriented Anatomy. 8th ed. Philadelphia: Lippincott Williams & Wilkins; 2017.
  3. [3] Dididze M, Tafti D, Sherman Al. Pronator Teres Syndrome. (Updated 2022 Jan 2). In: StatPearls (Internet). Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK526090/
  4. [4] Caetano EB, Vieira LÂ, Sprovieri FA, Petta GC, Nakasone MT, Serafim BL. Anatomical variations of pronator teres muscle: predispositional role for nerve entrapment. Rev Bras Ortop. 2017;52(2):169-175. Published 2017 Mar 2. doi:10.1016/j.rboe.2017.02.003
  5. [5] Van Hoecke J, Pérot C, Goubel F. Contribution des muscles biceps brachii et pronator teres á l’effort de prono-supination. I. Travail statique (Contribution of the biceps brachii and pronator teres muscles to the efforts of pronation or supination. I. Statistical work (author’s transl)). Eur J Appl Physiol Occup Physiol. 1978 Mar 20;38(2):83-91. French. doi: 10.1007/BF00421525. PMID: 639790.
  6. [6] Vymazalová K, Vargová L, Joukal M. Variability of the pronator teres muscle and its clinical significance. Rom J Morphol Embryol. 2015;56(3):1127-35. PMID: 26662149.

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