Stiffness after knee replacement can be a difficult problem to manage because finding the exact cause of the stiffness can sometimes be difficult, or because the stiffness is not due to a single factor, and it can be difficult to increase mobility without damaging the dynamics, which itself may cause the stiffness. Because stiffness is often accompanied by soft-tissue contractures, difficulties in wound closure may occur in the management of stiffness. In addition, some patients have high expectations and often still do not achieve the mobility they desire after surgery. When dealing with stiffness after total knee replacement, the first step is to find the cause and address it. Stiffness is managed with intensive rehabilitation under multimodal analgesia. Early stage of stiff knee can be based on intensive rehabilitation training under appropriate analgesic measures, including active and passive mobility training, CPM is a very effective rehabilitation measure. For patients with flexion contracture, sandbags can be used to straighten the knee joint, and if necessary, the knee joint can be immobilized in the extension position with a splint. 4 ~ 8 weeks after total knee replacement, if still in a stiff state, the simple rehabilitation training is difficult to work, need to be under anesthesia for manipulation release, in the process of manipulation release, be careful of periprosthetic fracture and patellar tendon avulsion. Patients more than 3 months after surgery. Rehabilitation and manipulation can no longer solve the problem, and surgical release is feasible, provided that the prosthesis is of appropriate size, normal position, normal force line, good stability, and exclude infection. Surgical release can be divided into arthroscopic release and incisional release. Arthroscopic release can remove the hyperplastic fibrous tissue, but the surgical instrument is easy to scratch the surface of patellar prosthesis, it is not recommended to use, and often need to be used in conjunction with manipulative release, incisional release can completely remove the hyperplastic fibrous tissue, and it can be combined with the quadriceps tendon molding surgery to improve the range of motion. Excess bone spurs or cement remains. Bone spurs as well as residual cement cause irritation to the soft tissues and increase the tension in the joint capsule, preventing the joint from fully straightening and preventing the joint from maximizing flexion. A medial medial parapatellar incision is recommended for stiffness release after total knee replacement. This incision makes it easier to deal with the quadriceps tendon and the osteotomy at the tibial tuberosity, and it is easier to deal with all parts of the knee joint. The areas that often require intraoperative release are the suprapatellar bursa, the medial and lateral compartments, and the peripatellar tendon fat pad. If, after intraoperative release of the above areas, knee flexion is still difficult because the extensor mechanism is too tight, or even if release of the above areas cannot be accomplished because the extensor mechanism is too tight, then quadriceps tendinoplasty or tibial tuberosity osteotomy is recommended. Quadriceps tendinoplasty is easier to perform, and the quadriceps can be lengthened appropriately, and in most cases it can be exposed sufficiently, but this procedure decreases the strength of the quadriceps muscle, and the knee joint needs to be protected from patellar necrosis in the postoperative period. However, this procedure reduces the strength of the quadriceps and requires postoperative protection of the knee joint to prevent the risk of patellar necrosis, and is therefore most often used in cases where the tibial tuberosity is not of good bone quality. Tibial tuberosity osteotomy allows for wider surgical exposure and preserves the blood supply to the fat pad, and postoperative bone-to-bone healing is fast and reliable. The patellar tendon stop can be moved up and down. If the surgical management is not successful and there is an abnormal position of the prosthesis, inappropriate size, inappropriate thickness of the spacer, loosening of the prosthesis, joint instability, incorrect osteotomy, abnormal joint planes, etc., then revision surgery is required. Revision surgery is required to completely remove the proliferating fibrous tissue and can be combined with quadriceps tendonoplasty to improve range of motion. Replacement of a thin tibial spacer alone is difficult to improve mobility and can be used in combination with other measures. Whether it is a revision or primary replacement, if a patient has a small range of motion after intraoperative suturing of the joint capsule, he or she should never expect to improve it with postoperative functional exercises. From the time of surgery until the knee reaches optimal function after surgery: it is a race between scar tissue formation and range of motion, so functional training after knee arthroplasty cannot be taken slowly, but must be done before scar tissue formation to achieve the desired range of motion of the knee, and the range of motion in the early postoperative period determines the final range of motion!