What Is Flexor Carpi Ulnaris Muscle

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.

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.


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