Flexor carpi ulnaris muscle

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Flexor carpi ulnaris
Dorsal (left) and ventral (right) views of deep muscles of the forearm. FCU is visible in blue.
Origin Medial epicondyle (common flexor tendon) and medial margin on olecranon of ulna
Insertion Pisiform, hook of the hamate, base of the fifth metacarpal bone
Artery Ulnar artery
Nerve Muscular branches of ulnar nerve
Nerve root C8 and T1
Actions Flexion and adduction of wrist
Antagonist Extensor carpi radialis brevis muscle and extensor carpi radialis longus muscle
Latin Musculus flexor carpi ulnaris
TA A04.6.02.030
FMA 38465
Anatomical terms of muscle

The flexor carpi ulnaris muscle (or FCU) is a muscle of the human forearm that acts to flex and adduct (medial deviation) the hand.

Origin and insertion[edit]

Flexor carpi ulnaris muscle arises by two heads, humeral and ulnar, connected by a tendinous arch beneath which the ulnar nerve and artery pass.

  • The humeral head arises from the medial epicondyle of the humerus by the common flexor tendon.
  • The ulnar head arises from the medial margin of the olecranon of the ulna and from the upper two-thirds of the dorsal border of the ulna by an aponeurosis.

Its insertion is into the pisiform bone and then via ligaments into the hamate bone-g pisohamate ligament- and 5th metacarpal bone-forming pisometacarpal ligament. Its action is to flex and adduct the wrist joint.


The flexor carpi ulnaris muscle is innervated by the ulnar nerve which has its roots in the C8 and T1 spinal nerves.


The tendon of flexor carpi ulnaris can be seen on the anterior of the distal forearm. On a person's distal forearm, right before the wrist, there will be either two or three tendons. The tendon of the flexor carpi ulnaris is the most medial (closest to the little finger) of these. The most lateral one is the tendon of flexor carpi radialis muscle, and the middle one, not always present, is the tendon of palmaris longus.


The muscle, like all flexors of the forearm, can be strengthened by exercises that resist its flexion. A wrist roller can be used and wrist curls with dumbbells can also be performed. These exercises are used to prevent injury to the ulnar collateral ligament of elbow joint.


Ulnar entrapment by the aponeurosis of the two heads of the flexor carpi ulnaris (FCU) muscle may cause cubital tunnel syndrome.

Additional images[edit]

External links[edit]