Flexor Carpi Ulnaris

Forearm · Upper Limb

The Flexor Carpi Ulnaris is a Upper Limb muscle within the Forearm group. It arises from Humeral head: medial epicondyle; Ulnar head: olecranon and posterior border of ulna and attaches to Pisiform, hook of hamate, and base of 5th metacarpal. When it contracts, it flexion and adduction (ulnar deviation) of wrist. Its nerve supply is the Ulnar nerve (C7, C8).

Origin, Insertion, Action & Nerve

Origin

Humeral head: medial epicondyle; Ulnar head: olecranon and posterior border of ulna

Insertion

Pisiform, hook of hamate, and base of 5th metacarpal

Action

Flexion and adduction (ulnar deviation) of wrist

Nerve

Ulnar nerve (C7, C8)

Attachments explained

The Flexor Carpi Ulnaris is defined first by where it attaches. Its origin is the more fixed anchor, usually the proximal or more stable end that stays put during contraction, while its insertion is the more mobile point that is pulled toward the origin when the muscle shortens.

Origin

Humeral head: medial epicondyle; Ulnar head: olecranon and posterior border of ulna

Insertion

Pisiform, hook of hamate, and base of 5th metacarpal

Action & function

When the Flexor Carpi Ulnaris contracts, it produces the following movement: Flexion and adduction (ulnar deviation) of wrist.

As part of the Forearm group of the Upper Limb, it works alongside neighbouring muscles to generate smooth, coordinated movement and to stabilise the structures it acts on.

Nerve supply & clinical relevance

The Flexor Carpi Ulnaris receives its nerve supply from the Ulnar nerve (C7, C8). This nerve carries fibres from spinal segment(s) C7, C8.

Because a muscle can only contract when its nerve is intact, injury to the Ulnar nerve or to its spinal roots (C7, C8) can weaken or paralyse the Flexor Carpi Ulnaris, impairing the movements it normally produces (flexion and adduction (ulnar deviation) of wrist). This is why knowing the innervation is central to localising nerve lesions in clinical practice.

How to study the Flexor Carpi Ulnaris (the OIANS method)

OIANS stands for Origin, Insertion, Action and Nerve, the four facts that uniquely define every skeletal muscle. To learn the Flexor Carpi Ulnaris, work through them in order: picture its origin, trace the muscle to its insertion, reason out the action that shortening between those two points must create, then add the nerve that drives it.

Most students remember the Flexor Carpi Ulnaris fastest by linking its action back to its attachments rather than memorising each fact in isolation. Once the origin and insertion make sense, the action usually follows logically.