The ECRB is the primary wrist extensor active during gripping, running through the second extensor compartment to the third metacarpal base. Its central position between the radial and ulnar wrist axes produces pure extension without deviation. At its lateral epicondyle origin it is the primary pathological tendon in lateral epicondylalgia (tennis elbow), with histological changes of angiofibroblastic degeneration.
| Origin | Lateral epicondyle via the common extensor origin |
|---|---|
| Insertion | Dorsal base of the third metacarpal |
| Nerve Supply | Deep branch of the radial nerve / posterior interosseous nerve (C7, C8) |
| Blood Supply | Radial artery |
| Actions | Pure wrist extension without deviation; Stabilises the wrist in the power grip position |
|---|
ECRB activates with every grip because wrist extension is needed to prevent the flexors from collapsing the wrist during finger flexion. This sustained activation during repetitive gripping explains the chronic overuse pattern of lateral epicondylalgia.
Lateral epicondylalgia (tennis elbow) affects the ECRB origin in 85-90% of cases. Eccentric wrist extension exercises, corticosteroid injection, and PRP all target this origin. Surgical ECRB debridement excises the pathological tissue from the lateral epicondyle.
The ECRB tendon is palpable in the second extensor compartment on the dorsoradial wrist during resisted wrist extension.
ECRB origin angiofibroblastic degeneration producing lateral elbow pain with resisted wrist extension, managed with eccentric loading and injection.
