The ECRL originates from the lateral supracondylar ridge (not the epicondyle) alongside the brachioradialis, making it one of the forearm muscles innervated by the radial nerve proper rather than the posterior interosseous nerve. Its second metacarpal insertion produces combined wrist extension and radial deviation — the motion used in backhand tennis strokes. It is the primary wrist extensor active during power grip.
| Origin | Lateral supracondylar ridge of the humerus and lateral intermuscular septum |
|---|---|
| Insertion | Dorsal base of the second metacarpal |
| Nerve Supply | Radial nerve (C6, C7) — before the nerve divides into deep and superficial branches |
| Blood Supply | Radial artery |
| Actions | Wrist extension; Radial deviation of the wrist |
|---|
During power grip, ECRL activates strongly to maintain wrist extension against the wrist flexion force produced by the long finger flexors — the reciprocal activation that produces the power grip position and prevents wrist collapse during strong grasp.
ECRL is preserved in posterior interosseous nerve palsy because it is supplied by the radial nerve proper proximal to the posterior interosseous nerve division at the arcade of Frohse. Radial nerve palsy at the lateral epicondyle level therefore produces wrist drop with preserved radial deviation (ECRL active) but lost extension without deviation (ECRB, ECU lost).
The ECRL is palpable on the dorsoradial forearm proximal to the ECRB, becoming firm during resisted wrist extension with the forearm supinated and becoming more prominent during radial deviation with extension.
Overuse injury producing dorsoradial forearm pain managed conservatively.
