Purpose To examine the changes in knee cartilage T2 values over 24 months in subjects with and without risk factors for knee osteoarthritis (OA) and their association with focal knee lesions at baseline. Materials and Methods Forty-one subjects without, and 101 subjects with OA risk factors (such as history of knee injury or surgery) were selected from the Osteoarthritis Initiative database (age: 45-55 years, no radiographic OA in the right knee). Baseline MR images of the right knee were assessed for prevalence and grade of focal knee lesions. Right knee cartilage T2 measurements were performed in five compartments (patella, medial/lateral femur/tibia) at baseline and 24 month follow-up. Results Compared to subjects without OA risk factors, those with OA risk factors showed no significant differences in baseline prevalence and grade of focal knee lesions (p>0.05), but had significantly higher T2 values in the medial femur compartment at both time points (p<0.05). T2 values averaged over all five compartments increased significantly over 24 months in both groups, but differences in T2 increase between the groups were not significant. Subjects with cartilage lesions showed significantly higher T2 values compared to subjects without cartilage lesions at both time points, but no accelerated T2 increase over 24 months (p>0.05). Conclusion Cartilage T2 values significantly increased over 24 months in subjects with and without OA risk factors, but neither the presence of OA risk factors nor the presence of cartilage lesions at baseline were associated with these T2 increases.

Objective To study the role of vastus lateralis/vastus medialis cross-sectional area ratio (VL/VM CSA ratio) in preclinical knee osteoarthritis (OA) using MRI-based cartilage T2 mapping technique and morphological analysis at 3.0T in non-symptomatic, middle-aged subjects. Material and Methods 174 non-symptomatic individuals aged 45–55 years with OA risk factors were selected from the Osteoarthritis Initiative incidence cohort. OA-related knee abnormalities were analyzed using the whole-organ MR imaging score (WORMS). Knee cartilage T2 maps were generated using sagittal 2D multiecho spin echo images of the right knee. Cross-sectional area (CSA) of thigh muscles was measured using axial T1W images of the right mid thigh. Spline-based segmentation of cartilage and muscles was performed on a SUN/SPARC workstation. Muscle measurements were normalized to body size using body surface area. Statistical significance was determined using Student’s t-test, Pearson correlation test, and multiple regression models. To correct for multiple testing, Bonferroni adjustments were applied across all tests within each of the primary results tables (Tables 3 – 7). Results Higher T2 values were associated with increased prevalence and severity of cartilage degeneration. In our study, male and female subjects with higher VL/VM CSA ratio demonstrated significantly lower mean cartilage T2 values (all compartments combined) (mean 44.10 versus 45.17, p = 0.0017), and significantly lower WORMS scores (mean 14.12 versus 18.68, p = 0.0316). Regression analyses of combined mean cartilage T2 using VL/VM CSA ratio as a continuous predictor showed a significant curvilinear relationship between these two variables (p = 0. 0.0082). Conclusion Our results suggested that higher VL/VM CSA ratio is associated with lower T2 values and decreased presence and severity of OA-related morphological changes. Additional studies will be needed to determine causality.

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