[Osteoid osteoma of the olecranon].

We report a case of osteoid osteoma of the olecranon which developed in the greater sigmoid cavity. The patient was a 22-year-old male who complained of arthritic-like symptoms limited to the elbow joint and progressing for three years. Rheumatoid arthritis then tuberculosis were entertained as possible diagnoses. The diagnosis of osteoid osteoma was not established until the disease had progressed for three years and had already become stiff due to epiphyseal remodeling. Resection of the nidus only alleviate pain and joint motion was not improved.