The Influence of Kinematic Alignment on Patellofemoral Joint Biomechanics in Total Knee Arthroplasty

Background: Anterior knee pain is a prevalent issue post total knee arthroplasty, often necessitating revision surgery. Various factors contribute to this complication, including patellar maltracking and excessive patellofemoral load. Kinematic alignment has emerged as an alternative, showing promising outcomes in clinical studies. However, its impact on patellofemoral biomechanics needs to be more adequately understood. This study compared the effects of kinematically versus mechanically aligned total knee arthroplasty on patellofemoral joint biomechanics. Methods: Eight fresh-frozen human knee specimens underwent biomechanical testing in a knee rig setup, performing an active weight-loaded knee joint flexion of 30–130°. After the testing of native kinematics, kinematically and mechanically aligned total knee arthroplasty was performed using a medial pivot implant design without patellar resurfacing. Quadriceps force, retropatellar peak pressure and the retropatellar contact area were measured during knee flexion using a patellar pressure-sensitive film. Patella kinematics (shift and tilt) was tracked using an optoelectrical measurement system. Functional regressions were used to determine the influence of the alignment on the kinematics and loading of the knee joint. Results: Kinematically aligned total knee arthroplasty resulted in reduced quadriceps force during knee flexion compared to mechanically aligned total knee arthroplasty. Retropatellar peak pressure, retropatellar contact area and patella kinematics did not vary between the alignments. Conclusions: Kinematic alignment offers potential benefits in reducing quadriceps force during knee flexion, which may mitigate anterior knee pain risk. Further research is needed to elucidate its effects in varying anatomical conditions and alignment strategies.