Physical Activity Associates with T1rho MRI of Femoral Cartilage Following Anterior Cruciate Ligament Reconstruction

Abstract

ABSTRACT Purpose Less physical activity has been associated with systemic biomarkers of cartilage breakdown following anterior cruciate ligament reconstruction (ACLR). Yet, previous research lacks analysis of deleterious cartilage compositional changes and objective physical activity following ACLR. The purpose of this study was to determine the association between physical activity quantified via accelerometer-based measures of daily steps and time in moderate-to-vigorous physical activity (MVPA), and T1rho magnetic resonance imaging (MRI) of the femoral articular cartilage, a marker of proteoglycan density in individuals with ACLR. Methods Daily steps and MVPA were assessed over 7 days using an accelerometer worn on the hip in 26 individuals between 6-12 months following primary unilateral ACLR. Resting T1rho MRI were collected bilaterally, and T1rho MRI inter-limb ratios (ILR: ACLR limb/contralateral limb) were calculated for lateral and medial femoral condyle regions of interest. We conducted univariate linear regression analyses to determine associations between T1rho MRI ILRs and daily steps and MVPA with and without controlling for sex. Results Greater T1rho MRI ILR of the central lateral femoral condyle, indicative of less proteoglycan density in the ACLR limb, was associated with greater time in MVPA (R2 = 0.178, P = 0.032). Sex-adjusted models showed significant interaction terms between daily steps and sex in the anterior (P = 0.025), central (P = 0.002), and posterior (P = 0.002) medial femoral condyle. Conclusions Lesser physical activity may be a risk factor for maintaining cartilage health following ACLR; additionally, the relationship between physical activity and cartilage health may be different between males and females.