Summary
Origins
- Lateral supracondylar ridge of the 🦴 humerus
- Lateral intermuscular septum adjacent to brachioradialis
Insertions
- Dorsal base of the second metacarpal with a slip to the third metacarpal
Actions
- Extends the wrist while maintaining light finger flexion
- Abducts the hand toward the radial side with extensor carpi radialis brevis
The extensor carpi radialis longus descends along the lateral forearm from the lower supracondylar ridge of the humerus. Its fusiform belly sits beside the brachioradialis, and its long tendon passes beneath the extensor retinaculum to reach the base of the second metacarpal.
Acting with extensor carpi radialis brevis it extends the wrist and abducts the hand toward the radial side. The pair balances flexor carpi radialis during gripping, while extensor carpi ulnaris provides the ulnar counterforce. Its tendon shares the dorsal wrist corridor with the extensor digitorum, framing the radial edge of the extensor tendons. Because the radial nerve innervates the muscle before entering the posterior compartment, its strength often remains even when deeper extensors weaken.
Related Muscles
- extensor carpi radialis brevis
- brachioradialis
- extensor carpi ulnaris
- flexor carpi radialis
- extensor digitorum