Arising from the lower third of the lateral supracondylar ridge of the humerus the muscle passes down the forearm, behind brachioradialis and beneath the thumb muscles, to be inserted as a flattened tendon into the base of the second metacarpal.
Nerve supply of extensor carpi radialis longus:
By the radial nerve (C6, 7) above the elbow, before the posterior interosseous branch is given off
Action of extensor carpi radialis longus:
Its action is indicated by its name. It is indispensable in the action of ‘making a fist’, and its tendon can be felt and often seen when this is done.