The objective of this study was to compare retrograde intramedullary femoral nailing with supracondylar locked screw-plate fixation for the treatment of periprosthetic femur fractures following total knee arthroplasty. Time to union and full weight bearing were the primary study outcomes, with perioperative blood loss, need for transfusion, need for revision surgery, and infection being the secondary outcomes. A retrospective review of 63 patients who sustained Rorabeck Type II periprosthetic femoral fractures was undertaken. Patients were pooled from 3 academic institutions between 2001 and 2009. Patients eligible for the study were identified from the electronic medical record using an IDX query of International Classification of Diseases 9 and Current Procedural Terminology codes for fixation of femur fracture with intramedullary implant or plate and screws. In the series, 35 patients were treated with intramedullary femoral nailing and 28 with a locked screw-plate. The 2 groups were compared for radiographic union at 6, 12, 24, and 36 weeks. At 36 weeks, radiographic union was significantly greater in the locked screw-plate group. Time to full weight bearing was not significantly different. A greater perioperative transfusion rate was observed in the locking plate group, but it also had an overall lower rate of reoperation, for any reason, compared with the intramedullary femoral nailing group. The results support the use of a laterally based locked plate in the treatment of Rorabeck type II distal femur periprosthetic fractures.