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Flexor carpi ulnaris muscle

Recommended video: Anterior compartment forearm muscles [11:53]
Attachments, innervation, functions and related clinical anatomy of the muscles of the anterior compartment of the forearm.
Flexor carpi ulnaris muscle (Musculus flexor carpi ulnaris)

Flexor carpi ulnaris is a fusiform muscle located in the anterior compartment of the forearm. It belongs to the superficial flexors of the forearm, along with pronator teres, palmaris longus, flexor digitorum superficialis and flexor carpi radialis. Flexor carpi ulnaris is the most medial of the superficial flexors.

Together with other muscles of the anterior forearm, flexor carpi ulnaris flexes the hand at the wrist. Besides flexing the hand, flexor carpi ulnaris is also involved in adduction of the hand at the wrist. 

This article will discuss the anatomy and function of the flexor carpi ulnaris muscle.

Key facts about the flexor carpi ulnaris muscle
Origin Medial epicondyle of humerus, olecranon and posterior border of ulna
Insertion Pisiform bone, hamate bone, base of metacarpal bone 5
Action Wrist joint: Wrist flexion, wrist adduction
Innervation Ulnar nerve (C7-T1)
Blood Supply Posterior ulnar recurrent artery, ulnar artery
  1. Origin and insertion
  2. Relations
  3. Innervation
  4. Blood supply
  5. Function
  6. Sources
+ Show all

Origin and insertion

Flexor carpi ulnaris originates with two heads which are linked by a tendinous arch. The heads are named according to the bones they attach to;

  • The smaller humeral head arises from the common flexor origin on the medial epicondyle of humerus.
  • The more extensive ulnar head originates from the olecranon and proximal part of the posterior border of ulna

As the muscle fibers pass towards the wrist joint, they converge on a long tendon in the distal part of the forearm. This tendon passes into the palmar surface of the hand to insert onto the pisiform and hamate carpal bones, as well as onto the base of the fifth metacarpal bone.

Why not pause and see what you already know about the flexors of the forearm with our quiz!


The tendon of flexor carpi ulnaris can be seen and palpated beneath the skin immediately proximal to the wrist joint. It is the most medial of the tendons that are visible superficially in this region.

Flexor carpi ulnaris lies superficial to flexor digitorum superficialis and medial to palmaris longus. As they pass into the forearm, the ulnar nerve and posterior ulnar recurrent artery pass deep to the tendinous arch between the humeral and ulnar heads of the muscle. Distally, the ulnar artery and ulnar nerve lie lateral to the tendon of flexor carpi ulnaris.


Innervation of the flexor carpi ulnaris muscle is from the brachial plexus via the ulnar nerve (C7-T1).

Blood supply

Flexor carpi ulnaris receives its arterial blood supply via three different routes. Proximally, a branch of the posterior ulnar recurrent artery supplies the muscle as it passes between the humeral and ulnar heads. Branches of the ulnar artery supply the middle and distal parts of the muscle, with an accessory supply also present distally via the inferior ulnar collateral artery.


Due to its position and direction in the forearm, flexor carpi ulnaris can move the hand sideways as well as flexing it. Contracting with flexor carpi radialis and palmaris longus, flexor carpi ulnaris produces flexion of the hand at the wrist joint.

However, when it contracts alongside the extensor carpi ulnaris muscle in the posterior compartment, their counteracting forces produce adduction of the hand at the wrist, otherwise known as ulnar deviation or ulnar flexion. 

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