Idiopathic Osteonecrosis of the Femoral Condyle Occurring in Two Sisters

Abstract

Spontaneous osteonecrosis of the knee was described as a distinct entity in 1968 (Ahlbäck et al) . The etiology of this lesion remains unknown, although micro-trauma and vascular insufficiency have been suggested as causes.
Typically the patient is a female in the sixth and seventh decade, sudden onset is characteristic, and the lesion occurs mainly on the medial femoral condyle. Radiographs show a subchondral radiolucency on the weight-bearing area with subsequent flattening, collapse and sclerosis.
We report on idiopathic osteonecrosis of the femoral condyle occurring in two sisters.