Flexor Carpi Ulnaris Muscle

Original Editor Uchechukwu Chukwuemeka

Top Contributors - Uchechukwu Chukwuemeka

Original Editor -

Top Contributors - Uchechukwu Chukwuemeka


Flexor carpi ulnaris muscle (FCU) is the most medial flexor muscles in the superficial compartment of the forearm[1]. It can adduct and flex the wrist at the same time; acts in tandem with FCR to flex the wrist and with the extensor carpi ulnaris to adduct the wrist. This muscle is the only muscle in the anterior compartment that is fully innervated by the ulnar nerve.



It has an long linear origin from olecranon and posterior border of the ulna,

A humeral head origin from the medial epicondyle of the humerus.


It inserts at the base of Pisiform bone, hook of hamate and base of 5th metacarpal.[1][2]


FCU is innervated by the Ulnar nerve (C7,C8, T1)


FCU blood supply is via ulnar collateral arteries, and also anterior and posterior ulnar recurrent arteries.


FCU flexes and adducts the hand at the wrist joint

Clinical Relevance[2]

The ulnar nerve enters the forearm by passing between the humeral and the ulnar heads of its origin.Compression and entrapment of the ulnar nerve can occur between the two heads of the Flexor carpi ulnaris  aponeurosis at the cubital tunnel; which a cap between the 2 heads of the Flexor carpi ulnaris[3].

Where the FCU tendon inserts serves as a landmark in finding the ulnar nerve and artery, which are on its lateral side at the wrist


Manual Muscle Testing[4]

The patient/client is seated with posterior aspect of the forearm and hand flat on a table; then, the hand is positioned in supination and extension

The therapist is seated at the side of the upper limb being tested, one hand stabilizes the patient's forearm and as well palpates the muscle and its tendon; while the other hand's two to three fingers is placed on the radial side of the hand at the 5th metacarpal and metacarpophalangeal joint of the patient

Instruction: The patient is instructed to abduct the little finger while flexing the wrist against the therapist's resistance. For further reading see...



  1. 1.0 1.1 Drake, RL, Vogl, W, Mitchell, AW, Gray, H. Gray's anatomy for Students 2nd ed.  Philadelphia : Churchill Livingstone/Elsevier, 2010
  2. 2.0 2.1 Moore, KL, Dalley, AF, Agur, AM. Clinically oriented anatomy. 7th ed. Baltimore, MD: Lippincott Williams & Wilkins, 2014
  3. Lung BE, Siwiec RM. Anatomy, Shoulder and Upper Limb, Forearm Flexor Carpi Ulnaris Muscle. Available from: https://www.ncbi.nlm.nih.gov/books/NBK526051/ (accessed 2nd April 2019)
  4. Hislop, HJ, Montgomery,J.  Daniels and Worthingham's Muscle Testing: Techniques of Manual Examination. 8th ed.  Missouri: Saunders Elsevier, 2007
  5. OTstudentVids. MMT of Flexor Carpi Radialis/Ulnaris and Extensor Carpi Uln. Available from: https://www.youtube.com/watch?v=31Wbe7xv8Jk [last accessed 29/3/2019]