Flexor carpi radialis muscle
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.
All these muscles share the function of flexing the hand on the wrist, which is why the entire compartment is also called the flexor compartment of the forearm. These muscles all have individual functions besides wrist flexion, and those of the flexor carpi radialis are wrist flexion and wrist abduction.
|Medial epicondyle of humerus
|Bases of metacarpal bones 2-3
|Wrist joint: Wrist flexion, wrist abduction
|Median nerve (C6, C7)
|Anterior/posterior recurrent ulnar artery, radial artery
This article will discuss the anatomy and function of flexor carpi radialis muscle.
Origin and insertion
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 lies deep to the forearm skin and superficial to the flexor digitorum superficialis muscle. It is lateral to palmaris longus, while being medial to pronator teres in its proximal part and to brachioradialis in its distal part. In the hand, the attaching tendinous fibers lie deep to the oblique head of adductor pollicis muscle.
In relation to neurovascular structures, the proximal part of the muscle covers the median nerve, prior to it passing beneath the flexor digitorum superficialis muscle. Just proximally to the wrist, the radial artery runs between the tendons of flexor carpi radialis and brachioradialis muscles, marking a common site for its palpation in order to measure someone’s radial pulse.
Innervation to flexor carpi radialis comes from the medial and lateral cords of the brachial plexus via the median nerve (C6, C7).
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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.
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.
Test yourself on all flexors of the forearm with our quiz!
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