Knee Joint Rotation Axis Is More Laterally Rotated and Valgus Than We Previously Thought

Abstract Background: Currently, the patient satisfaction rate after receiving TKA is around 80% to 90% and there is still room for further improvement. With the aim to provide reference for improving TKA surgery, stereophotogrammetry was used in this study to evaluate knee joint kinematics.Methods: Multiple MRI images of knee joints flexed at 0, 10, 20... to 100 degrees were scanned in bilateral knees of 45 asymptomatic adult volunteers. After three-dimensional alignment of the femur, the displacement and rotation angles of the tibia flexed at different angles were measured. Contributing factors were tested using One-way ANOVA and chi-square test in SPSS 24.Results: 1)No contributing factors was found to influence rotation axis; 2) Within the range of motion at 0-100° of flexion, the rotation axis exhibited no significant displacement relative to the femur. 3) On the horizontal plane, the lateral rotation angle of knee joint axis was 4.91°±1.84°(3°~7°) relative to transepicondylar axis (TEA) and 7.84°±2.09° relative to posterior condylar axis (PCA); on the coronal plane, the valgus angle of knee joint axis was 3.38°±0.82°(2.5°~5°) relative to tibial plateau, and 6.53°±0.91°(5°~8°) relative to the perpendicular line of the lower limb force line. Conclusion: No contributing factors were found, but the rotation axis of the knee joint is more laterally rotated and valgus than previously thought. These findings may explain the research result of some current literatures, and may provide theoretical rationale for further improvement of knee prosthesis design.