Osteonecrosis of both knees in a woman with Crohn's disease

Figure 1 Plain film radiographs (bilateral knees) showing multiple bilateral hypotransparent areas.

Figure 2 Computed tomography showing multiple lacunar areas in the femurs and patellas.

Figure 3 Magnetic resonance imaging (bilateral knees, T1-weighted images, coronal view) showing areas and serpiginous rims of low signal intensity in the femurs, tibiae and patellas, characteristic of osteonecrosis.

Figure 4 Magnetic resonance imaging (bilateral knees, T2-weighted images, coronal view) showing prominent medullary infarcts.

Figure 5 Magnetic resonance imaging (T2-weighted images, axial view) showing low signal serpiginous rims.