Impending Atypical Femur Fracture Presenting as Painful Total Knee Arthroplasty: A Report of 2 Cases

We report on 2 patients with atypical femur fractures that initially presented as painful total knee arthroplasties. There was a history of long-term bisphosphonate use in each case. Knee radiographs and laboratory studies were normal, and the patients were managed conservatively. Both subsequently sustained atypical femur fractures and underwent surgical stabilization.

Referred pain from a bisphosphonate-related femoral stress fracture can masquerade as pain about a total knee arthroplasty. This should be included in the differential diagnosis in at-risk patients because it can result in an atypical femoral shaft fracture above the prosthesis if not properly treated.