The lesion was characterized as an osteoid osteoma after a histopathological report.

Osteoid osteomas are benign tumors. They usually have a typical radiographic appearance of a central lucent nidus with surrounding sclerosis. Intra- and juxta-articular osteoid osteomas, however, may not have the usual radiographic features. In this case, the typical surrounding sclerosis was not present, difficulting the initial diagnosis.

Case contributed by: Dr Marcelo Bragança and Dr Flávia Costa