An unusual case of unilateral supernumerary extensor carpi radialis muscle.

An uncommon anatomical variant of muscle that can be considered as a supernumerary extensor carpi radialis muscle was found during the dissection of the forearm region. The identified extensor carpi radialis muscle has origin on the lateral supraepicondylar ridge of the humerus, and an unusual insertion on the tubercle of the scaphoid bone. The presence of this supernumerary muscle may cause diagnostic errors in the forearm region, and can produce a debilitating pain syndrome by secondary compression of adjacent nerves, vessels or tendons due to its course along the anterior compartment of the forearm.