Inability to bend a fractured knee may be the result of fracture complications such as joint stiffness, traumatic arthritis, and malunion of the fracture. Depending on the cause, rehabilitation exercises, surgical treatment, analgesic medication, and re-alignment treatment can be performed under the guidance of the doctor. 1. Joint stiffness: patients can not bend their knees due to the contracture of the joint capsule and surrounding muscles caused by the prolonged immobilization of the knee after fracture, resulting in impaired joint movement. It can be gradually recovered through timely release of immobilization and functional rehabilitation exercises, while arthroscopic minimally invasive surgery can be used to loosen the joint if the joint stiffness cannot be recovered. 2. Traumatic arthritis: when the fracture occurs in the knee joint, the joint surface is damaged, and the joint surface is uneven after the fracture heals, and the friction between the joint and the bone causes severe pain when the knee is bent, which makes the patient afraid to bend the knee. Non-steroidal anti-inflammatory drugs such as ibuprofen can be taken to relieve pain, and arthroscopic debridement or joint fusion can be performed in severe cases. 3. Fracture deformity healing: the fracture has not been reset, there are angular, rotational or overlapping deformities, affecting the function of the knee joint, resulting in the inability to bend the knee. The treatment is osteotomy or re-correction of the deformed part, and active rehabilitation exercise in the later stage. Therefore, the fracture of the knee can not bend should go to the hospital in time to improve the examination, clear the cause of the disease and then give targeted treatment.