Stress fracture of the tibia secondary to sports-related activities is relatively common, but rarely occurs secondary to osteoarthritis of the knee. Such fractures usually involve the proximal tibia. We report a 61-year-old woman with osteoarthritis and severe varus deformity of the knee who had a stress fracture of the distal tibial shaft. The patient had declined total knee replacement for severe osteoarthritis. She developed a stress fracture that subsequently malunited. The patient presented late and the diagnosis was not made for several months. The pathomechanics, diagnosis, and management options for this patient are discussed.