Flexor Carpi Ulnaris
Forearm · Upper Limb
The flexor carpi ulnaris is the most medial of the superficial forearm flexors. It has a humeral head from the medial epicondyle and an ulnar head from the olecranon and posterior border of the ulna, and it inserts onto the pisiform, the hook of the hamate, and the base of the fifth metacarpal. It flexes the wrist and adducts it (ulnar deviation), the two actions combining to angle the hand toward the little-finger side. Alone among the forearm flexors it is supplied by the ulnar nerve (C7, C8), which runs alongside it before entering the hand.
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)
Decode the name as you did for its radial counterpart: it flexes the wrist and, being ulnaris, deviates the hand toward the little-finger side. Its insertion onto the pisiform, hook of hamate, and fifth metacarpal keeps its pull firmly on the medial side of the wrist.
The fact that sets it apart is its nerve: it is the only forearm flexor supplied by the ulnar nerve rather than the median. The ulnar nerve runs alongside it into the hand, so learning this muscle doubles as a reminder of the nerve's course.
Frequently asked questions
Where is the Flexor Carpi Ulnaris located?
The Flexor Carpi Ulnaris is a muscle of the Forearm group, located in the Upper Limb.
What is the origin of the Flexor Carpi Ulnaris?
Humeral head: medial epicondyle; Ulnar head: olecranon and posterior border of ulna
What is the insertion of the Flexor Carpi Ulnaris?
Pisiform, hook of hamate, and base of 5th metacarpal
What movements does the Flexor Carpi Ulnaris produce?
Flexion and adduction (ulnar deviation) of wrist
What nerve supplies the Flexor Carpi Ulnaris?
Ulnar nerve (C7, C8)
Is the Flexor Carpi Ulnaris free to study in OIANS?
Yes. The Flexor Carpi Ulnaris is free in OIANS: its full origin, insertion, action and nerve details are open to everyone in the Muscle Directory, and because it belongs to the Upper Limb it is also covered by the free Quiz and Flashcard decks. The other regions, the "All Muscles" deck, and the Progress and Explore tools are unlocked with a one-time Lifetime purchase.
Related muscles
Study the Flexor Carpi Ulnaris
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