Objective To summarize the research progress on knee laxity of biomechanics and prevention and treatment after posterior cruciate ligament (PCL) reconstruction. MethodsThe domestic and international literature on the prevention and treatment of knee laxity after PCL reconstruction in recent years were extensively reviewed and analyzed. Results Different degrees of knee laxity often occur after PCL reconstruction, which can lead to poor prognosis in patients. The causes are associated with a variety of factors, including abnormal graft remodeling (such as differences in healing time and biomechanics among different types of grafts), tunnel position deviation (such as graft wear caused by the “killer turn” effect), and mechanical factors in postoperative rehabilitation (such as improper early weight-bearing and range of motion). These factors may promote graft elongation, increase early posterior tibial translation, and thereby induce knee laxity. ConclusionWhile PCL reconstruction improves knee stability, it is crucial to focus on and prevent postoperative knee laxity. However, current surgical methods are limited by factors such as graft characteristics, surgical technique flaws, and rehabilitation protocols, and thus cannot fully correct the issue of abnormal postoperative laxity. Surgical techniques and treatment strategies still need further improvement and optimization to enhance patients’ postoperative outcomes and quality of life.