[Osteoid osteoma of the sigmoid notch of the ulna]

We report one case of osteoid-osteoma (0.0.) developed in the radio-ulnar proximal joint in a young male adult. The initial diagnosis had been chronic epicondylitis evolving since two years. A surgical detachment of the muscle from the epicondylus lateralis humeri had even been performed with no result driving to contemplate again the initial diagnosis which was corrected by tomodensitometry and surgical exploration. Excision has obtained immediate pain relief and after a one year follow up there was no recurrence. The diagnostic problems raised by intra articular 0.0. of the elbow are discussed.