| 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 forearm Contributes to flexion of the forearm at the elbow |
| Nerve | Median nerve (C6-C7) |
| Artery | Branches of the bachial, radial and ulnar arteries |
Location & Overview
The pronator teres muscle is a forearm muscle with both radial 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 is shape and action. ‘Pronator’ refers to its action of pronation and ‘teres’ refers to its shape being long and rounded [3]
The median nerve most commonly 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, there are variations of this arrangement; where the median nerve passes through the muscle belly of the pronator teres’ ulnar head, or it is located posteriorly to both the muscle heads. Some individuals are also entirely missing the ulnar head of the pronator teres muscle (missing in around 14% of people in research performed by Caetano et al. [2017]) and in some individuals the ulnar head was very underdeveloped with just a fibrous band originating from the ulnar’s coronoid process (present in around 17% of the individuals investigated by Caetano et al. [2017]) [4]. Although the absence of the ulnar head is rare, in cases where it is absent, it may reduce the chance of median nerve entrapment [5].
Irritation of the median nerve caused by pronator teres syndrome can be caused by repetitive or fast grasping/pronation movements. Examples of such activities are: tennis, hammering, rowing and bodybuilders performing excessive exercise volume involving the aforementioned movements. These movements can lead to an entrapment of the median nerve and pronator teres syndrome. However, pronator teres syndrome is a relatively rare. Which can sometimes cause it to be mistaken or overlooked for more common conditions such as carpal tunnel syndrome [6].
Here we can see the pronator teres muscle in isolation from an anterior view.
Here we can see a more medial view of the pronator teres muscle. This allows us to see the two heads of origin: the larger humeral head and the smaller ulnar head.
Displayed here is a superficial view of the pronator teres muscle amongst the other muscles of the arm. You can see the brachioradialis muscle covers the distal part of the pronator teres.
Origin & Insertion
The humeral head is the largest of the two heads and originates from the superior part of the humerus’ medial epicondyle, on the medial supracondylar ridge. The smaller ulnar head originates from the ulna’s coronoid process. As the two heads travel down the forearm, they come together to form a common flexor tendon. This tendon then inserts into the middle of the shaft of the radius [7] [8] [9].
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.
Highlighted in blue we can see the insertion of the pronator teres on the lateral mid-shaft of the radius.
Actions
The pronator teres can perform pronation of the forearm as its main action. It is also able to assist in performing flexion of the forearm at the elbow joint [10] [11] [12].
Innervation
The median nerve innervates both heads of the pronator teres muscle from C6 to C7 roots [13] [14].
Blood Supply
Blood is supplied to the pronator teres muscle via the brachial, radial and ulnar arteries [15] [16].
Want some flashcards to help you remember this information? Then click the link below:
Pronator Teres Flashcards
References
| ↑1, ↑12, ↑14, ↑16 | 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, ↑9 | Moore KL, Agur AMR, Dalley AF. Clinically Oriented Anatomy. 8th ed. Philadelphia: Lippincot Williams & Wilkins; 2017. |
| ↑3, ↑5, ↑6, ↑7, ↑10, ↑13 | 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, ↑8 | 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 |
| ↑11 | 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. |
| ↑15 | 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. |
