Asymmetry in healthy adult knee kinematics revealed through biplane radiography of the full gait cycle.

Abstract

One commonly used criterion in evaluating a patients' response to knee surgery or rehabilitation is bilateral symmetry. However, the natural symmetry in uninjured healthy adult knee kinematics remains relatively unknown, making it challenging to determine if clinical treatment has adequately restored bilateral symmetry. The primary purpose of this study was to determine the typical side-to-side differences in 6 degree of freedom (DOF) knee kinematics over the entire gait cycle in healthy adults using biplane radiography. Six DOF tibiofemoral kinematics were measured during treadmill walking in 19 participants using a validated volumetric model-based tracking process that matched subject-specific bone models to biplane radiographs collected at 100 images/s. Average absolute side-to-side differences in knee kinematics at foot strike were 1.3 mm or less in translation and 3.8° or less in rotation. Peak side-to-side differences in knee kinematics occurred during the swing phase and were up to 2.2 mm in translation and 7.1° in rotation. Dominant versus non-dominant leg differences were 0.8 mm and 2.8° or less at foot strike and reached maximum values of 0.8 mm and 7.2° over the full gait cycle. Statement of Clinical Significance: This study quantifies the inherent asymmetry of knee kinematics in healthy individuals over the entire gait cycle. The values of asymmetry presented here may serve as a guide for evaluating functional outcomes and restoration of so-called "normal" kinematics after injury and clinical intervention. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.