Anatomy and Course
The flexor carpi radialis belongs to the superficial muscle group of the anterior forearm compartment.
- Origin (Origo): arises from the medial epicondyle of the humerus (epicondylus medialis humeri). Proximally, all muscles of this superficial group appear as a single common muscle head. Separation into distinct individual muscles becomes clearly visible more distally, at the junction of the upper and middle thirds of the forearm.
- Insertion (Insertio): the tendon of the muscle inserts onto the base of the second metacarpal bone, and occasionally sends a slip to the base of the third metacarpal bone.
- Tendon Features: on the radial side, the tendon passes beneath the deep fascia of the forearm. It is enclosed within a synovial sheath, the proximal end of which extends 1–2 cm above the superior margin of the flexor retinaculum (retinaculum musculorum flexorum).
Topography and Relations
In the superficial layer, from medial to lateral, the muscles are: the flexor carpi ulnaris, palmaris longus, flexor carpi radialis, and pronator teres.
- Relation to the Pronator Teres: the flexor carpi radialis overlies the distal part of the pronator teres (m. pronator teres), which courses deep toward the radius.
- Relation to the Brachioradialis: inferior to the pronator teres, the flexor carpi radialis approaches the brachioradialis (m. brachioradialis) at an acute angle and then runs parallel to it. The radial artery travels in the interval between them.
- Cross-Sectional View: in the middle third of the forearm, the muscle is visualized anteriorly alongside the superficial digital flexors, pronator teres, and palmaris longus.
- Surface Landmarks: the tendon of the flexor carpi radialis is clearly visible on the anterior aspect of the wrist joint, accompanied by three transverse skin creases and the tendon of the palmaris longus.
Blood Supply and Innervation
- Blood Supply: radial artery (a. radialis). During its course, the artery runs directly between the flexor carpi radialis and the brachioradialis.
- Innervation: median nerve (n. medianus, spinal cord segments C6–C8).
Functions
- Wrist flexion (palmar flexion).
- Radial deviation (abduction) of the wrist.
Clinical Significance
When mononeuropathies or nerve root compression are suspected, needle electromyography (EMG) is performed. The goal of this study is to assess the severity of denervation-reinnervation processes. The flexor carpi radialis is routinely included in the panel of tested muscles, along with the abductor pollicis brevis, flexor pollicis longus, flexor digitorum superficialis/profundus to digits II and III, and pronator teres.