ECRL has the most proximal radial nerve supply of any forearm extensor, arising directly from the radial nerve before it divides into superficial and deep (PIN) branches. This makes ECRL the most proximal muscle to test in radial nerve injuries.
| Origin | Lateral supracondylar ridge of the humerus — proximal end, above the lateral epicondyle |
|---|---|
| Insertion | Base of the second metacarpal — dorsal surface |
| Nerve Supply | Radial nerve (C6, C7) — branch arising above the lateral epicondyle |
| Blood Supply | Radial recurrent artery |
| Actions | Extends the wrist; Radially deviates the wrist — the primary wrist radial deviator; Assists elbow flexion via the lateral supracondylar ridge origin |
|---|
ECRL preservation with absent PIN function localises the radial nerve lesion to the PIN (posterior to the lateral epicondyle). ECRL is transferred in tendon transfer surgery to restore finger flexion (ECRL to FDP in high median + ulnar palsy). In de Quervain surgery, ECRL travels in the second extensor compartment alongside ECRB.
Palpated on the lateral forearm dorsum during resisted wrist extension with radial deviation.
Intact ECRL function in posterior interosseous nerve palsy distinguishing PIN entrapment from high radial nerve palsy — ECRL is spared because its nerve branch arises proximal to the PIN origin.
