Presentation
Painful right knee with fever, tenderness.
Patient Data
Well-defined eight-shaped lytic lesion of the distal femoral metaphysis surrounded by a thick dense rim of reactive sclerosis, oriented along the long axis of the bone and extending to the epiphysis through the growth plate.
On the MRI sequences the well-defined lesion has an intramedullary location within the femoral metaphysis, extending to the epiphysis through the growth plate. It displays a low signal on T1, heterogeneous high signal on PD fat sat and T2 with a peripheral rim isointense to muscle on T1, hypointense on PD fat sat and T2 with a regular enhancement "penumbra sign". No evidence of intra-articular extension. Mild surrounding bone marrow edema is noted.
Case Discussion
Radiographic and MRI features most consistent with Brodie abscess of the femoral metaphysis, extending to the epiphysis through the growth plate.