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Superficial flexors of the forearm

The superficial flexors of the forearm are a group of five muscles found at the anterior/ventral forearm. They form the surface of the ulnar side of the forearm where they can also be easily palpated. These muscles include:

  • Pronator teres muscle
  • Flexor carpi radialis muscle
  • Flexor carpi ulnaris muscle
  • Palmaris longus muscle
  • Flexor digitorum superficialis muscle

Their long tendons can be followed very well at the wrist joint, especially during flexion.

Key Facts
Pronator teres Origin: medial epicondyle of the humerus, coronoid process of the ulna
Insertion: lateral side of the radius
Actions: pronation of forearm, flexion of elbow
Antagonist: supinator muscle
Flexor carpi radialis Origin: common flexor tendon at the humerus
Insertion: bases of 2nd and 3rd metacarpal bones
Actions: flexion and abduction of wrist
Antagonist: extensor carpi ulnaris muscle
Flexor carpi ulnaris Origin: medial epicondyle of the humerus, olecranon of the ulna
Insertion: pisiform bone, hamate, base of the 5th metatarsal bone
Actions: flexion and adduction of wrist
Antagonists: extensor carpi radialis brevis et longus muscles
Palmaris longus Origin: common flexor tendon
Insertion: flexor retinaculum and palmar aponeurosis
Actions: flexion of wrist
Antagonists: extensor carpi radialis brevis et longus, extensor carpi ulnaris
Flexor digitorum superficialis Origin: medial epicondyle of the humerus, coronoid process of the ulna, radial tuberosity
Insertion: splits to 4 tendons, of which each one splits into a pair of 2; pairs insert on both sides of the middle phalanges of 2nd to 5th fingers
Actions: flexor of fingers at proximal interphalangeal joints
Antagonist: extensor digitorum muscle
Vascularization All supplied by the ulnar artery solely, except for the pronator teres which is supplied by both ulnar and radial arteries
Innervation All supplied by the median nerveexcept for the flexor carpi ulnaris that is supplied by the ulnar nerve
Clinical relations Medial epicondylitis, golfer's elbow

This article will discuss the anatomy of the superficial flexors of the forearm.

Anatomy and supply

All five muscles arise from the common flexor tendon located at the medial epicondyle of the humerus; some of them have additional attachment points on the radius and ulna.

The following muscles described are known to be the superficial flexors. 

Pronator teres muscle

The pronator teres muscle originates at the medial epicondyle of the humerus (humeral head) and coronoid process of the ulna (ulnar head). From there it courses under the brachioradialis and attaches to the lateral side of the radius, specifically at a roughening of the midshaft referred to as the pronator tuberosity. It is the most lateral of all the superficial flexors. (Innervation: median nerve (C6-C7))

Flexor carpi radialis muscle

This muscle runs from the common flexor tendon at the humerus to the bases of the second and third metacarpal bones.

(Innervation: median nerve (C6-C7))

Flexor carpi ulnaris muscle 

The flexor carpi ulnaris arises from the medial epicondyle of the humerus (humeral head) and the olecranon of the ulna (ulnar head).

The muscle has 3 insertion points: first, its tendon inserts into the pisiform bone, where the pisiform bone functions as a sesamoid bone; from there, it relays towards its other 2 insertion points at the hook of the hamate and the base of the 5th metacarpal bone. This muscle is the most medial of all superficial flexors and is mainly responsible for the contour of the ulnar side of the forearm.

(Innervation: ulnar nerve (C7-Th1))

Palmaris longus muscle

The palmaris longus is a very slender muscle originating from the common flexor tendon and inserting at the flexor retinaculum and palmar aponeurosis. This muscle is variable and can be, in some cases, missing on one or both arms or have an alternative course.
(Innervation: median nerve (C7-Th1))

Flexor digitorum superficialis muscle

The FDS has a large origin point attached to the medial epicondyle of the humerus (humeral head), the coronoid process of the ulna (ulnar head) and distally from the radial tuberosity (radial head). Its four insertion tendons split into two smaller end tendons each of which then insert on both sides of the middle phalanges of the second to fifth fingers. This is the deepest muscle of all superficial flexors. Innervation: median nerve (C7-Th1).

Innervation of the superficial flexors

All superficial flexors of the forearm are supplied by the median nerve except the flexor carpi ulnaris. In the elbow this nerve runs underneath the bicipital aponeurosis and between the two heads of the pronator teres.

From there, it courses under the flexor digitorum superficialis between the superficial and deep flexors and through the carpal tunnel at the wrist joint, and finally branches off into sensory and motor branches at the palm of the hand.

The carpal tunnel is a passage formed by the carpal bones and a densification of the antebrachial fascia (flexor retinaculum). In addition to the median nerve, the carpal tunnel also contains the tendons of the flexor digitorum superficialis, flexor digitorum profundus and flexor pollicis longus.

Recommended video: Superficial flexors of the forearm
Origins, insertions, innervation and functions of the superficial flexors of the forearm.

Function

The superficial flexors support various movements of the antebrachial and hand joints. As the name reveals, (almost) all of them do flexion of the wrist joint (except the pronator teres). Another thing these muscles have in common is that they are weak flexors of the elbow joint.

  • Furthermore, the pronator teres rotates the radius medially (pronation).
  • The contraction of the flexor carpi radialis moves the hand radially (radial abduction) whereas the flexor carpi ulnaris moves the hand ulnarly (ulnar abduction).
  • The flexor digitorum superficialis is involved in flexion of the metacarpophalangeal (MCP) and proximal interphalangeal joints (PIP) of the second to fifth finger.
  • The palmaris longus' major function is to support the palmar aponeurosis.

Clinical note

A chronic false strain of the superficial flexors often leads to inflammation and increased connective tissue in the common flexor tendon at the medial epicondyle of the humerus (medial epicondylitis).

Particularly golfers are affected by this condition as they permanently have to flex their hand wrist for the swing. For that reason, this condition is also referred to as the golfer’s elbow.

Classic symptoms are pain which increases during hand movements and trouble performing day-to-day tasks (e.g. pressing the door handle, hand shaking). Noticeably, adolescent baseball players often suffer from the medial epicondylitis as well (“little league elbow”). The reason is that children’s bones have ossification centers as they are still growing. When these experience massive false strain, the pressure is carried forward to the apophysis causing inflammation (apophysitis) or even deformation.

Superficial flexors of the forearm - want to learn more about it?

Our engaging videos, interactive quizzes, in-depth articles and HD atlas are here to get you top results faster.

Sign up for your free Kenhub account today and join over 852,397 successful anatomy students.

“I would honestly say that Kenhub cut my study time in half.” – Read more. Kim Bengochea Kim Bengochea, Regis University, Denver

Show references

References:

  • M. Schünke/E. Schulte/U. Schumacher: Prometheus – LernAtlas der Anatomie – Allgemeine Anatomie und Bewegungssystem, 2nd edition, Thieme Verlag (2007), p. 308-309
  • J. E. Muscolino: The muscular system manual – The skeletal muscles of the human body, 2nd edition, Elsevier Mosby (2005), p. 575-585, 589-591
  • M. S. Sater/A. S. Dharap/ M. F. Abu-Hijleh: The prevalence of absence of the palmaris longus muscle in the Bahraini population, Clinical Anatomy (November 2010), Issue 23(8), p. 956-961
  • H. Gray/ W. H .Lewis: Anatomy of the human body, 20th edition, Lea and Febiger (1918), p. 289 (http://www.bartleby.com/107/289.html)
  • J. Heisel: Neurologische Differenzialdiagnostik, Thieme Verlag (2007), p. 129-135
  • W. F. Frontera/J. K. Silver/T. D. Rizzo: Essentials of physical medicine and rehabilitation, 2nd edition, Saunders Elsevier (2008), p. 105-107

Author:

  • Achudhan Karunaharamoorthy

Illustrators:

  • Pronator teres - ventral view - Yousun Koh 
  • Flexor carpi radialis- ventral view - Yousun Koh 
  • Flexor carpi ulnaris- ventral view - Yousun Koh 
  • Flexor digitorum superficialis - ventral view - Yousun Koh 
  • Palmaris longus - ventral view - Yousun Koh 
  • Median nerve - ventral view - Begoña Rodriguez
  • Radial/Ulnar flexion - Paul Kim
  • Medial epicondyle of the humerus - ventral view - Yousun Koh 
© Unless stated otherwise, all content, including illustrations are exclusive property of Kenhub GmbH, and are protected by German and international copyright laws. All rights reserved.

Related Atlas Images

Flexors of the forearm

Extensors of the forearm

Radius and ulna

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