AP (above left) and lateral (above right) radiographs of the knee shows a serpiginous sclerotic lesion in the distal femur. Coronal T1 MRI without contrast of the knee (below left) shows the lesion in the distal femur to be defined by a focal serpentine low signal line with fatty center (reactive interface line) while coronal T2 MRI (below right) shows the lesion in the distal femur to be defined by a serpentine outer dark line and an inner bright line (double line sign).
