Where is the muscle located and how is it structured?
The flexor carpi radialis belongs to the superficial layer of forearm muscles located in the anterior compartment.
- Origin (Origo): originates from the medial epicondyle of the humerus (epicondylus medialis humeri). Proximally, all muscles of this layer appear as a single muscular head. Division into individual muscles becomes clearly noticeable more distally — at the border of the upper and middle thirds of the forearm.
- Insertion (Insertio): the tendon of the muscle attaches to the base of the 2nd metacarpal bone, occasionally to the base of the 3rd metacarpal bone.
- Tendon features: on the radial side, the tendon passes beneath the deep fascia of the forearm. It is surrounded by a synovial sheath, the upper end of which extends 1–2 cm above the upper margin of the flexor retinaculum (retinaculum musculorum flexorum).
Topography and adjacent structures
In the first layer, the muscles are arranged from the medial to the lateral side: flexor carpi ulnaris, palmaris longus, flexor carpi radialis, and pronator teres.
- Relation to the pronator teres: the flexor carpi radialis covers the distal part of the pronator teres (m. pronator teres), which passes deep toward the radius.
- Relation to the brachioradialis: beyond the pronator teres, the muscle approaches the brachioradialis (m. brachioradialis) at an angle and then runs parallel to it. The radial artery runs between them.
- On transverse section: in the middle third of the forearm, the muscle is visualized anteriorly along with the flexor digitorum superficialis, pronator teres, and palmaris longus.
- External landmarks: on the anterior surface of the wrist joint, the tendon of the flexor carpi radialis is visible along with three transverse skin creases and the tendon of the palmaris longus.
Blood supply and innervation
- Blood supply: radial artery (a. radialis). Along its course, the artery runs between the flexor carpi radialis and the brachioradialis.
- Innervation: median nerve — n. medianus (spinal cord segments C6–C8).
What is its function?
- Wrist flexion.
- Radial abduction of the hand.
Clinical significance
If mononeuropathy is suspected, needle electromyography (EMG) is performed. The purpose of this study is to assess the severity of the denervation-reinnervation process. The flexor carpi radialis is among the muscles examined, along with the abductor pollicis brevis, flexor pollicis longus, flexors of the 2nd and 3rd digits, and pronator teres.
Class and exam questions
Where does the flexor carpi radialis originate?
The muscle originates from the medial epicondyle of the humerus, similarly to the other muscles of the first (superficial) layer of the forearm.
Where does the tendon of this muscle pass?
The tendon passes beneath the deep fascia on the radial side, is surrounded by a synovial sheath, and inserts into the base of the 2nd, and occasionally 3rd, metacarpal bone.
What major vessel runs near the flexor carpi radialis?
The radial artery (a. radialis) runs between the brachioradialis and the flexor carpi radialis.
What else to study on this topic
- Median nerve (n. medianus)
- Radial artery (a. radialis)
- Pronator teres (m. pronator teres)
- Flexor retinaculum (retinaculum musculorum flexorum)
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