The association of physical activity and progression of knee cartilage T2 relaxation time with 3 Tesla MRI over a period of 4 years using data from the osteoarthritis initiative

Purpose: The relationship of physical activity with the development of osteoarthritis remains unclear. The purpose of this study was to investigate the association between physical activity levels and early degenerative cartilage changes at the knee, measured using T2 relaxation times over a period of 4 years using 3 Tesla (3T). Materials and Methods: 152 subjects without radiographic or symptomatic knee osteoarthritis were randomly selected from the Osteoarthritis Initiative (OAI) database. The inclusion criteria included 45-60 years of age, BMI of 19-27 kg/ m2, and no knee pain in either knee (WOMAC score of zero), and a Kellgren-Lawrence (KL) score less than 2 in the right knee at baseline. The Physical Activity Scale for the Elderly (PASE) was completed at the initial visit and was used to categorize individuals into quartiles (Q1, Q2, Q3, Q4). T2 of articular cartilage in different locations in the knee was measured from multi-echo SE, a sequence acquired in the right knee of each individual from baseline and 48-month follow-up visits. Multiple linear regression models were used to adjust for age, gender, and BMI to determine the association between physical activity level and progression of knee T2 relaxation time. Results: Very high (Q4) and very low (Q1) physical activity levels were associated with higher T2 progression than a mid-level of physical activity (Q3) in the lateral femur (p = 0.025, p = 0.032, respectively). In the medial femur, very high levels of physical activity (Q4) were associated with higher T2 progression than a mid-level of physical activity (Q3, p = 0.015), while differences over lower levels of physical activity (Q2, Q3) trended toward significance (p = 0.084, p = 0.098, respectively). Conclusion: Very high levels of physical activity, as measured by PASE, were associated with higher progression of knee T2 values in the lateral and medial femur. Low levels of physical activity were associated with higher progression in the lateral femur. This suggests that both very low levels of physical activity and high levels of physical activity may predispose asymptomatic, middle-aged individuals to increased biochemical changes suggestive of cartilage degradation over time. These findings need to be confirmed in other cohorts and using objective measures of physical activity.