Migration of the nail into the adjacent articular space may be seen due to loosening in the long term as Kuntscher nails are lockless nails. Migration of an intramedullary nail into the knee in a patient who had had femur shaft fracture fifteen years ago due to a gun shot injury and had been treated with Kuntscher nail caused septic arthritis by carrying the drainage developing from osteomyelitis of femoral diaphysis into the articular space. Septic arthritis developing due to the migration of nail into the knee is an extremely rare complication. This case emphasizes the need for removal of Kuntscher nails just after the completion of the fracture union.