Patients can’t straighten their legs after falling on their knees, it is not necessarily self-healing, the details are as follows: First, it can be self-healing: for mild injuries, there is soft tissue swelling, affecting the leg straightening, after local braking and rest, it can be eliminated gradually, and the knee joint can be restored to straighten. Secondly, it can not be self-healing: if it is a serious knee injury, such as patella fracture and dislocation, meniscus tear, resulting in the knee joint can not be straightened, it can not be self-healing, and it needs to be treated, using surgical incision and reduction of internal fixation, as well as arthroscopic minimally invasive surgical suture of meniscus, to restore the flatness of the meniscus and fracture of the alignment, alignment, in order to solve the intra-articular lesions, so that the patient’s knee joint after the operation can be straighten. Therefore, whether the leg cannot be straightened after a knee fall can be healed by itself needs to be judged according to the severity of the injury, and if it is more serious then it usually cannot be healed by itself.