Recognizing and identifying osteolysis around total knee arthroplasty.

Osteolysis around total knee arthroplasty can be difficult to identify because it typically occurs in cancellous bone of the distal femur and proximal tibia, which has a low radiodensity, and because it is often obscured on radiographs by the metallic prosthesis. Careful evaluation is warranted in circumstances where osteolysis is likely: radiographically evident polyethylene wear, high-activity young patients with a prosthesis in place for a long time period, or implant designs associated with osteolysis. Osteolysis of the distal femur is best seen on lateral radiographs and often involves the posterior condyles; on anteroposterior radiographs it may be seen as radiolucency extending proximally into either condyle. Osteolysis of the tibia often occurs along access tracks such as screws or around the periphery of well-fixed implants. Three-dimensional imaging modalities with new metal suppression technology hold the promise of improving accuracy of osteolysis detection in the near future.