Femoral Condyle Subchondral Insufficiency Fracture (The diagnosis formerly known as Spontaneous Osteonecrosis of the Knee)! Insufficiency subchondral fracture of the femoral condyle is commonly seen in elderly women with decreased bone density. The insufficiency fracture is usually visible at the weight bearing subchondral bone of the medial femoral condyle as a small region of decreased T1 and T2 signal intensity. There is usually extensive edema throughout the femoral condyle. For many years we’ve been calling similar findings of diffuse condyle edema in the adult as spontaneous osteonecrosis of the knee (SONK). Today we know that these cases of extensive edema are usually due to a small insufficiency subchondral fracture and not necrosis of the bone. The small subchondral fracture can progress to osteonecrosis due to increased intra osseous pressure, but the fracture is the predisposing factor (the egg came before the chicken!). Note that in these cases we don’t see the typical serpiginous linear abnormality in signal intensity that we classically see with AVN/osteonecrosis. When you see diffuse edema of the medial femoral condyle, pay close attention to the subchondral bone and more often than not, you’ll find that small insufficiency fracture. Leave the term SONK behind and call it subchondral insufficiency fracture of the knee – it’s more elegant!