Supracondylar fractures in patients with total knee prostheses are challenging surgical problems for which there has been no single satisfactory method of management. The authors present four cases to show that a fully cannulated, closed-section, stainless steel supracondylar intramedullary nail can be inserted in a closed fashion through a 3 cm longitudinal patellar splitting incision between the metal condyles of a nonconstrained femoral component of a total knee prosthesis. The nail can be interlocked with percutaneous screws and provides primary stability of a supracondylar femoral fracture, even in the presence of total knee and total hip prostheses.