This is the first report of extensive bilateral patellar tendon ossification occurring over a prolonged time after a unilateral knee injury. An 84-year-old Japanese man with a spinal cord injury caused by a burst fracture of the T12 vertebra presented with a bony hard prominence on the left knee, which was injured in a traffic accident when he was 77 years old. Radiography revealed extensive ossification of the bilateral patellar tendons. We review the English literature with a focus on the localization of bilateral heterotopic ossification of the knee in patients who had a central nervous system injury.