Flexor Carpi Radialis
The flexor carpi radialis is a superficial forearm muscle that is involved in flexion and abduction of the hand.
The name of this muscle consists of three parts. The word flexor is derived from the Latin flectere, which means “to bend.” Carpi comes from carpus, meaning “wrist.” Radialis simply refers to the location of the flexor carpi radialis on the radial side of the forearm.
On the anterior aspect of the forearm, the flexor carpi radialis is the closest visible tendon to the thumb when the wrist is in a fully flexed position.
The flexor carpi radialis lies at the lateral end of the flexor retinaculum of the hand – also known as the transverse carpal ligament - on the greater multangular between the points where the ligament attaches to the bone.
The flexor retinaculum is significant in the present context due to its involvement in carpal tunnel syndrome. Inflammation of one of the nine carpal tendons (including the flexor carpi radialis) creates pressure against the flexor retinaculum. Because it is a ligament; a piece of strong connective tissue, its ability to stretch is limited so it cannot provide the space necessary to relieve pressure caused by inflamed tendons. This ultimately results in the pressure being impacted upon the median nerve, leading to the symptoms known as carpal tunnel syndrome.
Carpal tunnel surgery will typically target the flexor retinaculum, where the carpal transverse ligament is usually cut to release pressure on the median nerve, if non-surgical treatments have proven ineffective.
The flexor carpi radialis originates at the medial epicondyle of the humerus, running alongside the flexor digitorum superficialis.
Anterior aspect of the second metacarpal, with slips to the third metacarpal and trapezial tuberosity.
The flexor carpi radialis provides flexion and abduction of the hand at the wrist.
A 1991 study showed that carpal tunnel surgery combined with local steroid injections was effective in minimizing long-term disability caused by the spontaneous rupture of the flexor carpi radialis tendon associated with scapho-trapezio-trapezoid arthritis.
Tonkin MA, Stern HS, Spontaneous rupture of the flexor carpi radialis tendon, J Hand Surg Br. 1991 Feb;16(1):72-4
Flexor carpi radialis exercises
Any exercise that involves abducting the wrist (moving the wrist towards the side of your thumb) against resistance will strengthen the flexor carpi radialis.
Rest your hand on a table with your thumb facing up. Resist moving your hand in the direction of your thumb. The hand should not move. This is a strengthening exercise for the wrist, forearm and elbow.
Perform 15 repetitions each side, holding the resistance for five seconds each.
McConathy (1981), Structure-function Relationships of the Flexor Carpi Radialis Muscle Compared Between Four Mammalian Species