What Is Flexor Carpi Ulnaris Muscle

Last updated: February 8, 2026Reviewed date: February 8, 2026Reading time: 4 min read

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Article Summary

What Is Flexor Carpi Ulnaris Muscle/Flexor Carpi Ulnaris Muscle is a superficial flexor muscle of the forearm that flexes and adducts the hand. It is the most powerful wrist flexor. Flexor carpi ulnaris originates from 2 separate heads connected by a tendinous arch. The humeral head arises from a flexor tendon origin on the medial epicondyle, while the ulnar head arises from the olecranon and...

Key Takeaways

This article explains Origin and Insertion of Flexor Carpi Ulnaris Muscle in simple medical language.
This article explains Blood Supply of Flexor Carpi Ulnaris Muscle in simple medical language.
This article explains Nerves of Flexor Carpi Ulnaris in simple medical language.
This article explains Functions of Flexor Carpi Ulnaris Muscle in simple medical language.

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Definition

What Is Flexor Carpi Ulnaris Muscle/Flexor Carpi Ulnaris Muscle is a superficial flexor muscle of the forearm that flexes and adducts the hand. It is the most powerful wrist flexor. Flexor carpi ulnaris originates from 2 separate heads connected by a tendinous arch. The humeral head arises from a flexor tendon origin on the medial epicondyle, while the ulnar head arises from the olecranon and upper three-fourths of the subcutaneous border of the ulna by an aponeurosis. Flexor carpi ulnaris inserts on the fifth metacarpal bone, the hook of hamate, and the pisiform bone of the wrist. Flexor carpi ulnaris inserts into the hook of hamate through the pisohamate ligament and inserts into the 5 metacarpal bone through the pisometacarpal ligament.[rx]

Flexor carpi radialis is a fusiform muscle located in the anterior forearm. It belongs to the superficial layer of the anterior forearm compartment, along with the pronator teres, flexor carpi ulnaris, palmaris longus and flexor digitorum superficialis muscles.

Origin and Insertion of Flexor Carpi Ulnaris Muscle

Flexor carpi radialis originates from the medial epicondyle of humerus, via the common flexor tendon, and surrounding fascia (antebrachial fascia and intermuscular septa). This common flexor tendon is a common origin for the six long flexor muscles in the forearm; flexor carpi radialis, palmaris longus, flexor carpi ulnaris, pronator teres, flexor digitorum superficialis and profundus.

From the medial epicondyle, the muscle belly courses obliquely, crossing from the ulnar to the radial part of the forearm. In the lower third of the forearm, it gives off a long tendon that passes below the flexor retinaculum into the palmar surface of the hand. Within the flexor retinacular space, the tendon passes through its own synovial sheath. It then crosses the palmar surface of the scaphoid bone and traverses in a groove on the surface of the trapezium bone. The tendon then inserts to the palmar surface of the bases of metacarpal bones 2-3.

Flexor carpi radialis

Origin: medial epicondyle of humerus via common flexor tendon
Insertion: base of 2nd metacarpal
Action: flexion and abduction of the hand
Innervation: median nerve

Blood Supply of Flexor Carpi Ulnaris Muscle

Flexor carpi ulnaris is supplied by the ulnar collateral arteries and small ulnar artery branches. The ulnar artery reaches the flexor carpi ulnaris along the middle third of its muscle belly. Flexor carpi ulnaris lymphatic drainage is part of the upper limb lymph system consisting of superficial and deep lymphatic vessels.
The superficial vessels around the basilic vein go to the cubital lymph nodes, which are proximal to the medial epicondyle of the humerus. Vessels around the cephalic vein go to the axillary lymph nodes. The deep lymphatic vessels also drain lymph from the flexor carpi ulnaris and follow the major deep veins, eventually terminating in the humeral axillary lymph nodes.
Flexor carpi radialis is mostly supplied by a branch arising high in the forearm from the anterior or posterior recurrent ulnar arteries. The rest of its nutritional needs are fulfilled by 6-8 branches of the radial artery.

Nerves of Flexor Carpi Ulnaris

Flexor carpi ulnaris is innervated by the muscular branch of the ulnar nerve, C7, and C8. Unlike the median nerve, which passes between the 2 heads of the pronator teres, the ulnar nerve passes between the two heads of the flexor carpi ulnaris.
Innervation to flexor carpi radialis comes from the medial and lateral cords of the brachial plexus via the median nerve (C6, C7).

Functions of Flexor Carpi Ulnaris Muscle

Due to its oblique course, flexor carpi radialis pulls the hand proximally and laterally, meaning that it is able to produce the combined motion of wrist flexion and wrist abduction (radial deviation). Acting together with flexor carpi ulnaris and palmaris longus, it produces a balanced flexion of hand, i.e. flexion without abduction. However, when it works in synergy with extensor carpi radialis longus and brevis, the net result of their counteracting forces is a balanced hand abduction.

To a lesser extent, the muscle contributes to pronation as it obliquely crosses the forearm. It is also active during extension of the digits, preventing unwanted extension of the hand.

References

Safety note: This is not a prescription or diagnosis. For severe symptoms, pregnancy danger signs, children with serious illness, chest pain, breathing difficulty, stroke-like weakness, or major injury, seek urgent care.

Which doctor may help?

Start with a registered doctor or the nearest qualified health center.

What to tell the doctor

Write when the problem started and how it changed.
Bring old prescriptions, investigation reports, and current medicines.
Write allergies, pregnancy status, diabetes, kidney/liver disease, and major past illnesses.
Bring one family member if the patient is weak, elderly, confused, or a child.

Questions to ask

What is the most likely cause of my symptoms?
Which danger signs mean I should go to hospital quickly?
Which tests are necessary now, and which can wait?
How should I take medicines safely and what side effects should I watch for?
When should I come for follow-up?

Tests to discuss

Vital signs: temperature, pulse, blood pressure, oxygen saturation
Basic physical examination by a clinician
CBC, urine test, blood sugar, or imaging only when clinically needed

Avoid these mistakes

Do not use antibiotics, steroid tablets/injections, or strong painkillers without proper medical advice.
Do not hide pregnancy, kidney disease, ulcer, allergy, or blood thinner use.
Do not delay emergency care when danger signs are present.

Medicine safety and first-aid guide

This section is for patient education only. It does not replace a doctor, pharmacist, or emergency care.

Safe first steps

Rest, drink safe water, and observe symptoms carefully.
Keep a written note of symptoms, duration, temperature, medicines already taken, and allergy history.
Seek medical care quickly if symptoms are severe, worsening, or unusual for the patient.

OTC medicine safety

For mild pain or fever, ask a registered pharmacist or doctor before using common over-the-counter pain/fever medicines.
Do not combine multiple pain medicines without advice, especially if you have kidney disease, liver disease, stomach ulcer, asthma, pregnancy, or take blood thinners.
Do not give adult medicines to children unless a qualified clinician advises it.

Avoid these mistakes

Do not start antibiotics without a proper medical decision.
Do not use steroid tablets or injections casually for quick relief.
Do not delay emergency care because of home remedies.

Get urgent help if

Severe symptoms, confusion, fainting, breathing difficulty, chest pain, severe dehydration, or sudden weakness need urgent medical care.

Medicine names, dose, and timing must be decided by a qualified clinician or pharmacist after checking age, pregnancy, allergy, other diseases, and current medicines.

For rural patients and family caregivers

Patient health record and symptom diary

Write your symptoms, medicines already taken, test results, and questions before visiting a doctor. This note stays on your device unless you print or copy it.

Doctor to discuss: Doctor / qualified healthcare provider

Tests to discuss with doctor

Basic vital signs: temperature, pulse, blood pressure, oxygen level if needed
Relevant blood, urine, imaging, or specialist tests only after clinical assessment

Questions to ask

What is the most likely cause of my symptoms?
Which warning signs mean I should go to emergency care?
Which tests are really needed now?
Which medicines are safe for my age, pregnancy status, allergy, kidney/liver/stomach condition, and current medicines?

Emergency warning signs such as chest pain, severe breathing difficulty, sudden weakness, confusion, severe dehydration, major injury, or loss of bladder/bowel control need urgent medical care. Do not wait for online information.

Go to emergency care if you notice:

Severe or rapidly worsening symptoms
Breathing difficulty, chest pain, fainting, confusion, severe weakness, major injury, or severe dehydration

Doctor / service to discuss: Qualified healthcare provider; specialist depends on symptoms and examination.

Step 1
Check danger signs first
If danger signs are present, seek emergency care and do not wait for online information.
Step 2
Record the symptom story
Write when symptoms started, severity, medicines already taken, allergies, pregnancy status, and test results.
Step 3
Visit a qualified clinician
A doctor, nurse, or qualified healthcare provider can examine you and decide which tests or treatment are needed.
Step 4
Do only useful tests
Do tests after clinical assessment. Avoid unnecessary tests, random antibiotics, or repeated medicines without diagnosis.
Step 5
Follow up and return early if worse
If symptoms worsen, new warning signs appear, or treatment is not helping, return for review quickly.

Rural patient practical tips

Take a written symptom diary and all previous prescriptions/test reports.
Do not hide medicines already taken, even herbal or over-the-counter medicines.
Ask which warning signs mean urgent referral to hospital.

This roadmap is for education. A real diagnosis and treatment plan requires history, examination, and clinical judgment.

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