Effect of functional knee loading on articular cartilage MRI T2 relaxation time and thickness in patients at risk for knee osteoarthritis

The objectives of this study were: 1) to evaluate the effect of a functional loading stimulus on MRI-acquired T2 relaxation time (T2) and thickness of knee articular cartilage, and 2) to compare the response between patients at risk for knee OA and healthy controls. A total of 32 participants (16 healthy controls [24.7 ± 3.0 years], and 16 at-risk participants [37.5 ± 12.2]) underwent 3T MRI T2 mapping scans immediately before and after a standardized 25-minute functional loading stimulus on a computerized treadmill that included a variety of challenging walking conditions. Groups were defined using the Osteoarthritis Initiative Control (healthy) and Incidence Cohort (at-risk) Criteria. We analyzed changes in T2 between groups in the superficial and deep layers of tibiofemoral, patellar, and trochlear cartilage, and for tibiofemoral cartilage thickness using multivariate linear mixed-effects models. T2 was shorter in the superficial cartilage layers in both groups. The mean combined change (95 % confidence interval) in T2 of the superficial layer was -3.80 ms (-4.87; -2.73) for at-risk participants and -3.89 ms (-4.96; -2.82) for healthy controls. The between-group difference in change was 0.09 ms (-1.04; 1.22). There was a decrease in articular cartilage thickness in the lateral compartment for healthy controls (-0.14 mm [-0.24; -0.04]), otherwise there were no changes detected. Consistently shorter T2 was observed in the articular cartilage of patients at risk for knee OA and in healthy controls, after a challenging walking test, but with no concurrent change in cartilage thickness, suggesting a similar articular cartilage response to functional loading.