The extensor carpi radialis longus is the most proximal of the radial wrist extensors, originating above the common extensor attachment and passing through the second extensor compartment at Lister tubercle to the index metacarpal base. Along with the extensor carpi radialis brevis, it forms the most important wrist extensor group for power grip, maintaining the wrist in extension to maximise the mechanical advantage of the finger flexors during gripping tasks.
| Origin | Lateral supracondylar ridge of the humerus proximal to the common extensor origin |
|---|---|
| Insertion | Dorsal surface of the base of the second metacarpal |
| Nerve Supply | Radial nerve (C6, C7) |
| Blood Supply | Radial artery |
| Actions | Extension of the wrist; Radial deviation of the wrist; Weak assistance in elbow flexion |
|---|
The synergistic action of wrist extension by the ECRL and ECRB during grip increases finger flexor mechanical advantage by roughly 70 percent, which is why a dropped wrist from radial nerve palsy causes dramatic grip weakness even though the finger flexors themselves are intact.
The ECRL and ECRB tendons pass through the second extensor compartment together at Lister tubercle, where intersection syndrome occurs 4 to 6 centimetres proximal to the wrist at the crossing of the first and second compartments. This crossing produces the pain, swelling, and crepitus that is often mistaken for de Quervain tenosynovitis. The ECRL origin adjacent to the lateral epicondyle also contributes to lateral epicondylalgia.
The ECRL is palpable on the dorsoradial forearm as the more proximal and radial of the two radial wrist extensor tendons, identified by tracing from the lateral epicondylar ridge to the index metacarpal base.
Friction tenosynovitis at the crossing of the first and second extensor compartments 4 to 6 centimetres proximal to the wrist, producing dorsal forearm pain, swelling, and crepitus that worsens with repetitive wrist extension.
Degenerative tendinopathy at the ECRL and ECRB origins on the lateral epicondyle producing lateral elbow pain reproduced by resisted wrist extension and gripping.
