Surgical treatment of distal femoral osteosarcoma, shown here, was performed with expanded osteosarcoma resection and tumor knee prosthesis replacement. Due to timely treatment, the patient did not have osteosarcoma metastasis and had no tumor recurrence or metastasis and good joint function at 7 years of follow-up. It is hoped that patients with bone tumor can receive treatment as early as possible for early detection, so that they will get the best treatment effect.