[Overlooked osteosarcoma in a patient undergoing total knee arthroplasty. A case report].

A 72-year-old woman presented with pain, swelling, and decreased range of motion of the left knee joint after total knee arthroplasty in 2005. We performed standard x-rays, which were highly suspicious for an osteosarcoma of the distal femur; this was proven by open biopsy. Retrospectively, the x-rays taken before implantation of the prosthesis showed suspicious findings. Because the femur was tumor-contaminated, with the intramedullary adjustment far-reaching proximally, a limb salvage procedure was no longer possible. To improve function, we decided to perform a stump-lengthening procedure using a special implant. With regard to the dismal consequences, we recommend that every suspicious finding before an elective surgical procedure be examined with further diagnostics and, if necessary, histological confirmation.