One of the causes of large knee joint bone defects (LKJBD) is resection of non-viable bone fragments during debridement of open fractures or radical surgical intervention in focus of osteomyelitis. For weight-bearing restoration, these patients are recommended to receive multi-staged surgical treatment: reconstructive surgeries with Ilizarov bone transfer, or using combined methods. Objective - to present a case report of successful treatment of a female patient with 25 cm knee joint bone defect. Materials and methods. A female patient was born in 1993, had polytrauma and opened fracture of distal femur as a result of a traffic accident. After multiple debridement, a large defect of distal femur, proximal tibia and defect of soft tissues appeared. Multi-stage operative treatment using bone transport over the nail and lengthening over the nail were used. Results. The total period of treatment was 42 months (3.5 years). The total period of external fixation was 292 days (9.7 months). The patient had spent 197 days (6.5 months) in the hospital. The complications that arose didn't affect the duration and outcome of treatment. Conclusion. The use of lengthening over the nail and bone transport over the nail techniques can significantly reduce the external fixation period and, thus, reduce the number of complications associated with the «hyper-prolonged» use of external fixation by Ilizarov. The use of a shortening of the contralateral extremity can be a valid method of choice when treatment of limb lengths discrepancy.