It is difficult to maintain the initial posterior stability of the knee after posterior cruciate ligament reconstruction. Residual posterior knee laxity after operation is a problem of PCL reconstruction. It not only results in abnormal kinematics of the knee, but also leads to secondary meniscus injury and cartilage degeneration of the affected knee, and eventually leads to knee osteoarthritis, which may especially happen with persistent and severe posterior laxity. The main reasons of residual posterior knee laxity after PCL reconstruction are: improper treatment of the posterolateral corner injury, poor positioning of the femoral tunnel, small tibial slope, and unreasonable postoperative rehabilitation. There are some concepts and technologies, such as using artificial ligaments, tibial tunnel fixation with suspensory device or suspensory device combined with interference screws, enlargement of graft diameter, all-inside reconstruction combined suture augmentation, slow and gradual postoperative rehabilitation, which can eliminate or reduce the postoperative residual laxity, in order to improve clinical outcomes after PCL reconstruction. For the patients with flat tibial slopes, double-bundle PCL reconstruction and concurrent slope-increasing tibial osteotomy is suggested. It can reduce the risk of posterior laxity and improve the stability of the knee after operation.

The reconstruction of the posterior cruciate ligament (PCL) through the tibial tunnel is the most commonly used reconstruction technique after ligament injury.However, when the graft passes through the tibial tunnel back to the medial condyle of the femur, a sharp angle is formed at the proximal end of the tibia, called the "killer turn". The existence of the "killer turn" can lead to graft wear and expansion of adjacent tibial tunnel after PCL reconstruction, affecting the stability of the posterior knee joint after operation and even leading to the failure of operation. There are several techniques, such as modifified tibial tunnel technique which the proximal exit of tibial tunnel is located in the inferior and lateral aspect of the PCL tibial anatomic insertion site, increasing the angle between the tibial tunnel and the tibial plateau, creating a tibial tunnel from the anterior lateral side of the tibia, remnant preserving as soft tissue cushion, and inlay and onlay techniques for reconstructing PCL without using tibial tunnel reconstruction, can reduce the "killer turn" effect. The above 6 techniques, theoretically, can effectively reduce or eliminate the "killer turn" effect and improve the posterior stability of the knee joint after PCL reconstruction, so as to improve the clinical efficacy of PCL reconstruction. But, the number of cases using these techniques is relatively small, and their effectiveness, reliability, and advantages and disadvantages for patients still need more clinical practice to further explore and verify.