The Biomechanical Effect of Posterior Cruciate Ligament Reconstruction on Knee Joint Function

Background The effectiveness of posterior cruciate ligament reconstruction in restoring normal kinematics under physiologic loading is unknown. Hypothesis Posterior cruciate ligament reconstruction does not restore normal knee kinematics under muscle loading. Study Design In vitro biomechanical study. Methods Kinematics of knees with an intact, resected, and reconstructed posterior cruciate ligament were measured by a robotic testing system under simulated muscle loads. Anteroposterior tibial translation and internal-external tibial rotation were measured at 0°, 30°, 60°, 90°, and 120° of flexion under posterior drawer loading, quadriceps muscle loading, and combined quadriceps and hamstring muscle loading. Results Reconstruction reduced the additional posterior tibial translation caused by ligament deficiency at all flexion angles tested under posterior drawer loading. Ligament deficiency increased external rotation and posterior translation at angles higher than 60° of flexion when simulated muscle loading was applied. Posterior cruciate ligament reconstruction reduced the posterior translation and external rotation observed in posterior cruciate ligament-deficient knees at higher flexion angles, but differences were not significant. Conclusion Under physiologic loading conditions, posterior cruciate ligament reconstruction does not restore six degree of freedom knee kinematics. Clinical Relevance Abnormal knee kinematics may lead to development of long-term knee arthrosis.