18-yo male with left hip pain for 3 months.
Coronal, axial, and sagittal fat sat PD-WI (first image) demonstrate moderate/extensive area of bone marrow edema in the anteromedial acetabulum with questionable sclerosis internally; there is no clearly defined focal bone lesion. Coronal, axial, and sagittal reformatted CT images (second image) show a radiolucent lesion with central calcification in the subchondral bone of the superomedial acetabulum (arrows), as well as subtle perilesional reactive sclerosis. These findings are consistent with an intra-articular osteoid osteoma (OO) of the hip.
Juxtaarticular/intra-articular OO may be difficult to diagnose because they are often subperiosteal or centrally located and not infrequently found in anatomically complex regions. The hip is the most common site of intra-articular OO, often with inflammatory signs that may simulate primary monoarthritis.
