Assessing Risk and Progression of Knee Osteoarthritis via Loading Rate and T2 Mapping of Cartilage

Knee osteoarthritis (OA) is a progressive degenerative disease in which the articular cartilage gradually wears away. Cartilage failure has been shown to result from repetitive impulsive loadings. People experiencing large loading rates as a result of imprecise limb control at heelstrike during gait are thus considered at a higher risk. However, high loading rate does not necessarily predict knee OA as the mechanical strength of the cartilage, characterized by the fiber network and water content, is not considered. MR T2 mapping helps bridge the gap as it is sensitive to the changes in the structure and water content of the cartilage. T2 mapping values increase with increased age and OA. Quantification of the relationship between T2 mapping values and loading rates may help better assess the risk and progression of knee OA. We will address this issue by measuring T2 map of the cartilage, joint kinematics, joint kinetics, loading rates and muscle activity using gait and MRI analysis in 40 subjects with knee OA (KL II & III) and 40 healthy controls under different loading and cartilage conditions, i.e. after 30-min standing, 30-min resting and 30-min walking, with two-year follow-up study with the same research protocol. This project will be carried out in three years with the following specific tasks and goals: U1st YearU: to determinate the relationships between gait variables (spatial-temporal variables, loading and unloading rates of the vertical GRF and the joint axial forces, EMG data, and kinematics and kinetics of the joints) during functional activities and MRI T2*values in the knee cartilage. U2nd YearU: to determinate the differences of structure, mechanical loadings, gait variables in the knee among after long-term loading and unloading conditions will be compared through MRI and gait analysis techniques. Data analysis of the baseline study and manuscript preparation of the baseline study will be performed for submission. U3rd YearU: Two years follow-up (longitudinal) study will be performed. The long-term changes of structure, mechanical loadings, joint kinematics, and joint kinetics in the OA and normal knee between different loading conditions will be compared through MRI and gait analysis techniques. We hypothesize that (1) the OA group would show greater loading rates and T2 mapping values than the controls, especially after prolonged loading; (2) patients with greater loading rates and T2 mapping values would show increased knee OA progression rate. A new protocol for knee OA risk and progression assessment will be developed based on the results.