Ulnar head of flexor carpi ulnaris

At a glance

English

Ulnar head of flexor carpi ulnaris

Latin (TA2)

Caput ulnare flexoris ulnaris carpi

System

Muscle

Region

Upper limb

Side

Paired, left and right

About the ulnar head of flexor carpi ulnaris

Flexor carpi ulnaris is the most medial muscle of the superficial layer on the front of the forearm, lying along the little-finger side. It has two heads. The humeral head is small and comes from the medial epicondyle by the common flexor tendon; the ulnar head is broader and longer, taken from the olecranon and from much of the ulna's back border.

The ulnar head starts on the medial edge of the olecranon and continues by an aponeurosis along the ulna's posterior border for its upper two-thirds, shared with extensor carpi ulnaris and flexor digitorum profundus. Its fibres slope down and forwards to join those of the humeral head in one belly. The tendon forms along the front of the lower forearm and ends on the pisiform. Ligaments carry the pull onward: the pisohamate ligament to the hook of the hamate and the pisometacarpal ligament to the base of the fifth metacarpal.

Between the two heads is a tendinous arch, and the ulnar nerve passes beneath it, leaving the groove behind the medial epicondyle to enter the forearm. This is the cubital tunnel. Bending the elbow tightens the arch and narrows the tunnel, so it is the commonest place for ulnar nerve compression, giving tingling in the ring and little fingers and later weakness of the small hand muscles. Lower down the posterior ulnar recurrent artery runs between the heads, and the ulnar artery and nerve lie under the muscle's lateral edge.

The muscle flexes the wrist and moves the hand towards the ulnar side; acting with extensor carpi ulnaris it gives pure ulnar deviation. It is a strong muscle for its size and helps fix the wrist during forceful gripping and during actions such as hammering.

Attachments, action and supply

Origin

Olecranon, medial edge, and the upper two-thirds of the posterior border of the ulna, through a shared aponeurosis.

Insertion

Pisiform, and through the pisohamate and pisometacarpal ligaments, the hook of the hamate and the base of the fifth metacarpal.

Action

Flexes the wrist and moves the hand towards the ulnar side; steadies the wrist in a strong grip.

Nerve supply

Ulnar nerve (C7, C8, T1).

Blood supply

Posterior ulnar recurrent artery and muscular branches of the ulnar artery.