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Repeatability of an Integrative Method to Assess Knee Joint Mechanics and Cartilage Health under Load



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An integrative and repeatable method that assesses quantitative magnetic resonance imaging (qMRI), mechanical measures by MRI (mechMRI) and gait (kinetics and kinematics) parameters is needed to better understand the mechanics of ACL-injury which is an early model of post-traumatic osteoarthritis. In developing a method that can be used, this research sought to answer three major questions: 1) What is the repeatability of the qMRI, mechMRI and gait analysis measures in healthy individuals? 2) What is the repeatability of the kinematic and kinetic outcomes using a MRI-based anatomical system and a standard gait coordinate system? 3) Is there a link between contact area and qMRI T2 relaxation times in cartilage? Addressing the above research questions involved primarily assessing the repeatability of each measure, expressed as the root-mean squared standard deviation (SDrms), as well as evaluating novel measures to determine the link between the different metrics. A MRI-safe loading rig was designed to simulate loading at the knee joint during MRI scanning as well as MRI-lucent gait markers to create a common coordinate system between the MRI and gait systems. Data was collected three times within a week for five healthy participants for this repeatability study. At the gait lab, participants carried out five motion tasks including walking, stair ascent, descent and chair rise and sit. With the MRI-lucent gait markers still at the same position, qMRI T2 relaxation time and anatomical MRI scans were carried out. The scans were acquired while the knee was unloaded and fully extended as well as loaded in two flexed positions. The repeatability results showed a link between qMRI T2 relaxation times and contact areas with low-SDrms measures in some qMRI-contact integration metrics and coordinate methods of processing dynamic data. qMRI-contact integration metrics were found to have smaller SDrms values for loaded cartilage in the lateral region (Average SDrms: 2.2 ms). Walk peak abduction angle had the smallest SDrms value for kinematics (0.8 degrees) and walk peak flexion moment for the kinetic measures (0.04 N.m/kg). Between dynamic data processed with MRI-based anatomical coordinates and standard gait coordinates systems, functional-based was generally found to have the smaller SDrms values. MRI-based processed data showed smaller SDrms values in kinetic outcome measures compared to that acquired from the standard gait coordinate system. In conclusion, there are indeed measures across the three different metrics that have smaller SDrms values and therefore may be better suited for use in the study of the ACL-injured population. From the findings of this study, we recommend particular attention be paid to lateral and loaded cartilage conditions for contact mechanics and qMRI T2 evaluation, and that knee kinematics and kinetics be evaluated with standard gait coordinate system, for the study of healthy and ACL-injured individuals.



ACL-injury, Osteoarthritis, Repeatability study



Master of Science (M.Sc.)


Mechanical Engineering


Mechanical Engineering



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