A case of acute traumatic subluxation of the extensor carpi ulnaris tendon as it passes through the sixth compartment of the wrist is described. The literature suggests that acute injuries can be treated for 6 weeks in a long arm cast, with the forearm in pronation and slight radial deviation and dorsiflexion, but there are no case reports described. The findings in this case suggest that for optimal results, surgical repair of the retaining fibro-osseous sheath of the extensor carpi ulnaris is preferable over the nonoperative cast technique.