The authors describe one case of post-traumatic dislocation of the extensor carpi ulnaris tendon. They found eleven other cases reported in the literature. The type of lesion should be looked for in cases of trauma to the wrist without a bony lesion. The treatment should be surgical when function is impaired, either shortly after the initial trauma or if the dislocation becomes habitual. The aim is to reconstruct a tendon sheath. The results were generally satisfactory.