Higher Body Mass Index Is Associated With Biochemical Changes in Knee Articular Cartilage After Marathon Running: A Quantitative T2-Relaxation MRI Study

Abstract

Background: More than 30 million individuals participate in marathon running every year worldwide. As the popularity of marathon running continues to increase, it is essential for the purposes of injury prevention to understand the effects of marathon running on the knee cartilage. Purpose: To investigate the immediate effects of marathon running on knee articular cartilage and to determine the relationship between body mass index and cartilage biochemical composition. Study Design: Descriptive laboratory study. Methods: T2-relaxation magnetic resonance imaging (MRI) of knees in 18 nonprofessional marathoners (mean age, 35.6 ± 6.4 years) was performed before and after a full-length marathon. Three-dimensional models of the knee articular cartilage were reconstructed and divided into different regions of interest. The 3-dimensional models were then applied to corresponding T2-relaxation MRI maps to calculate T2 values in each region of interest. The mean values of the T2-relaxation times in each region of interest before and after the marathon were compared by use of the paired Student t test. The Pearson correlation coefficient between T2 change and runner body mass index (BMI) was calculated. Results: Postmarathon T2-relaxation times were significantly higher than premarathon values for patellofemoral cartilage (32.6 ± 12.1 vs 34.1 ± 10.9 ms; P