Intra-articular osteoid osteoma of the distal humerus: a diagnostic challenge.

Osteoid osteoma rarely presents in an intra-articular or juxta-articular location, leading to synovitis and flexion deformity, which can easily mislead the diagnosis. We present a case of an intra-articular osteoid osteoma of the distal humerus in a 19-year-old woman with pain and flexion deformity of the elbow. Although radiographs were normal, a nidus was demonstrated on CT scan. Appropriate surgical treatment provided relief to the patient and the diagnosis was confirmed on histopathology. Thus, an intra-articular osteoid osteoma may be mistaken for more common causes of synovitis unless there is an index of suspicion and appropriate imaging is undertaken.