Extensor carpi radialis longus arises from the lateral humerus, extending and abducting the wrist.
The extensor carpi radialis longus is a superficial muscle of the posterior compartment of the forearm. It primarily extends and abducts the wrist. Positioned lateral to the extensor carpi radialis brevis, it contributes to wrist movements and provides dynamic stability during grip and lifting activities.
The extensor carpi radialis longus is located on the lateral side of the posterior forearm. It emerges from the lateral supracondylar ridge of the humerus and runs down to the base of the second metacarpal bone.
The muscle has a long, fusiform belly that narrows into a strong tendon distally. It lies superficial throughout its course and is partly covered by the brachioradialis in the proximal forearm.
The extensor carpi radialis longus contributes to:
The muscle is innervated by the radial nerve (C6–C7), specifically from a branch before the radial nerve divides into superficial and deep branches.
In the upper forearm, the extensor carpi radialis longus lies adjacent to the brachioradialis. As it descends, it runs lateral to the extensor carpi radialis brevis. The radial nerve passes deep to the muscle near its origin.
The muscle and its tendon can often be seen or palpated on the lateral side of the forearm, especially during active wrist extension and abduction. Its tendon lies just medial to the brachioradialis at the wrist.
The extensor carpi radialis longus develops from the extensor muscle mass of the posterior forearm bud, which originates from paraxial mesoderm during embryogenesis. Its radial nerve innervation is consistent with its origin from the dorsal muscle group.
In some primates and quadrupeds, the extensor carpi radialis longus is more developed due to its role in limb support and locomotion. In humans, it has evolved to assist in precision grip and coordinated wrist movement.