Flexor Carpi Ulnaris Muscle Anatomy

Overview
Origin Humeral head: Medial epicondyle of humerus via common flexor tendon
Ulnar head: Olecranon and upper 2/3 of posterior border of ulna
Insertion Pisiform bone
Hamate bone
Base of fifth metacarpal bone
Action Flexes hand at wrist joint
Adduction of hand at wrist joint
Very weak flexion of the elbow joint
Nerve Ulnar nerve (C7,C8, T1)
Artery Ulnar artery
Ulnar recurrent artery

Location & Overview

The flexor carpi ulnaris muscle is the most powerful wrist flexor. It has two heads, a humeral head and an ulnar head, which are linked by a tendinous arch. It is located in the anterior compartment of the forearm. It is one of the superficial flexor muscles of the forearm and the most medial of these superficial flexor muscles. The other superficial forearm flexors are: the palmaris longus, pronator teres, flexor carpi radialis, and the flexor digitorum superficialis [1].

flexor carpi ulnaris from a superficial view

Here we can see the flexor carpi ulnaris from a superficial view amongst the other muscles of the arm. The flexor carpi ulnaris is highlighted in green on the medial side of the forearm.

flexor carpi ulnaris from an anterior view

Here we can see the flexor carpi ulnaris from an anterior view (the front of the body).

flexor carpi ulnaris from a posterior view

Here we can see the flexor carpi ulnaris from a posterior view (the back of the body).

Origin & Insertion

The flexor carpi ulnaris muscle has two heads, a humeral head and an ulnar head. These two heads arise at the origin points of this muscle. The humeral head originates from the common flexor tendon, on the medial epicondyle of the humerus. The ulnar head originates from the olecranon and the upper two thirds of the posterior border of the ulna. The two heads converge via a tendonous arch. The muscle then continues down the forearm crossing the wrist joint to insert onto the fifth metacarpal bone, the hook of hamate, and the pisiform bone of the wrist. The flexor carpi ulnaris inserts into the hook of hamate through the pisohamate ligament and inserts into the fifth metacarpal bone through the pisometacarpal ligament [2] [3].

Flexor carpi ulnaris origin highlighted in red on the olecranon of the ulna and medial epicondyle of the humerus

Here we can see the origin points of the flexor carpi ulnaris. The origin is highlighted in red on the olecranon of the ulna and medial epicondyle of the humerus (via the common flexor tendon).

Flexor carpi ulnaris insertions highlighted in blue on the pisiform, hamate and fifth metacarpal bones

Here we can see the insertion points of the flexor carpi ulnaris. The insertions are highlighted in blue on the pisiform, hamate and fifth metacarpal bones.

Picture of the pisiform bone, hamate bone, fifth metacarpal bone, pisohamate ligament, and pisometacarpal ligament which are all colour coded

Here we can see the bones which the flexor carpi ulnaris inserts onto. These bones are colour coded for easy identification. We can also see the pisohamate ligament and the pisometacarpal ligament. The flexor carpi ulnaris inserts into the hamate through the pisohamate ligament and inserts into the fifth metacarpal bone through the pisometacarpal ligament.

This is why most depictions of this muscle do not show it connecting onto the hamate or the fifth metacarapal. The flexor carpi ulnaris does not directly connect to them. Rather, it is those two ligaments (which are is close proximity to the flexor carpi ulnaris) that are connecting these bones together and by proxy allowing the flexor carpi ulnaris to interact with them. However, these insertions on the hamate and fifth metacarpal are still considered insertions of the flexor carpi ulnaris.

Actions

The actions of the flexor carpi ulnaris are flexion and adduction of the hand at the wrist joint (radiocarpal joint). In addition to flexion and adduction, the flexor carpi ulnaris can also flex the elbow joint. However, it is very weak when it comes to elbow flexion and this is by no means a main action of the flexor carpi ulnaris [4] [5].

Innervation

The flexor carpi ulnaris is innervated by the muscular branch of the ulnar nerve (C7, C8, T1). The ulnar nerve passes between the two heads of the flexor carpi ulnaris [6] [7] [8] [9].

Blood Supply

Blood is supplied to the flexor carpi ulnaris primarily via the ulnar artery (86% of cases) and the recurrent ulnar artery (14% of cases). The ulnar artery arises from the brachial artery [10] [11].

Want some flashcards to help you remember this information? Then click the link below:
Flexor Carpi Ulnaris Flashcards

References

References
1, 2, 4, 6 Lung BE, Siwiec RM. Anatomy, Shoulder and Upper Limb, Forearm Flexor Carpi Ulnaris Muscle. [Updated 2022 Jun 28]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK526051/
3 Maroukis BL, Ogawa T, Rehim SA, Chung KC. Guyon canal: the evolution of clinical anatomy. J Hand Surg Am. 2015 Mar;40(3):560-5. doi: 10.1016/j.jhsa.2014.09.026. Epub 2014 Oct 29. PMID: 25446410; PMCID: PMC4791630.
5 Chaudhry M, Aminullah H, Sinkler MA, Arain A. Anatomy, Shoulder and Upper Limb, Forearm Compartments. 2022 Aug 1. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan–. PMID: 30969606.
7 Anderson TB, Bordoni B. Anatomy, Shoulder and Upper Limb, Forearm Nerves. 2022 Jul 25. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan–. PMID: 32119401.
8 Pyun SB, Kang S, Kwon HK. Anatomical and electrophysiological myotomes corresponding to the flexor carpi ulnaris muscle. J Korean Med Sci. 2010 Mar;25(3):454-7. doi: 10.3346/jkms.2010.25.3.454. Epub 2010 Feb 17. PMID: 20191047; PMCID: PMC2826750.
9, 10 Sharpe F, Barry P, Lin SD, Stevanovic M. Anatomic study of the flexor carpi ulnaris muscle and its application to soft tissue coverage of the elbow with clinical correlation. J Shoulder Elbow Surg. 2014 Jan;23(1):82-90. doi: 10.1016/j.jse.2013.07.057. PMID: 24331124.
11 Shen S, Pang J, Seneviratne S, Ashton MW, Corlett RJ, Taylor GI. A comparative anatomical study of brachioradialis and flexor carpi ulnaris muscles: implications for total tongue reconstruction. Plast Reconstr Surg. 2008 Mar;121(3):816-829. doi: 10.1097/01.prs.0000299920.14548.2a. PMID: 18317131.