Physical Activity and Spatial Differences in Medial Knee T1rho and T2 Relaxation Times in Knee Osteoarthritis

STUDY DESIGN: Cross-sectional. OBJECTIVES: To investigate the association between knee loading-related osteoarthritis (OA) risk factors Obesity, malalignment, and physical activity) and medial knee laminar (superficial and deep) T1rho and T2 relaxation times. BACKGROUND: The interaction of various modifiable loading-related knee risk factors and cartilage health in knee OA is currently not well known. METHODS: Participants with and without knee OA (n = 151) underwent magnetic resonance-imaging at 3 T for superficial and deep cartilage T1rho and T2 magnetic resonance relaxation times in the medial femur (MF) and medial tibia (MT). Other variables included radiographic Kellgren-Lawrence (KL) grade, alignment, pain and symptoms using the Knee injury and Osteoarthritis Outcome Score, and physical activity using the International Physical Activity Questionnaire (IPAQ). Individuals with a KL grade of 4 were excluded. Group differences were calculated using 1-way analysis of variance, adjusting for age and body mass index. Linear regression models were created with age, sex, body mass index, alignment, KL grade, and the IPAQ scores to predict the laminar Tlrho and T2 times. RESULTS: Total IPAQ scores were the only significant predictors among the loading-related variables for superficial MF Tlrho (P = .005), deep MT Tlrho (P = .026), and superficial MF T2 (P = .049). Additionally, the KL grade predicted the superficial ME Tlrho (P = .023) and deep MT Tlrho (P = .022). CONCLUSION: Higher physical activity levels and worse radiographic severity of knee OA, but not obesity or alignment, were associated with worse cartilage composition.