[A case of idiopathic aseptic osteonecrosis of the patellae: repeat study of Tc-99m HMDP bone scintigraphy in a reparative phase].

A 37-year-old woman entered our hospital because of bilateral knee pain. Tc-99m HMDP bone scintigram demonstrated increased activity in the bilateral patellae and cold lesion in the center and left lateral segments of the left patellae, so-called doughnut pattern. Trephine biopsy was performed to prove bilateral idiopathic asepct osteonecrosis of the patellae. The knee pain subsided and a bone scan 5 months later demonstrated increased activity in the bilateral patellae more widely than initial scan. We report the usefulness of Tc-99m HMDP bone scintigraphy to observe a reparative phase of idiopathic asepct osteonecrosis of the patellae.