15 runners were randomized to receive an intra-articular injection of hyaluronic acid or normal saline 1 week prior to a marathon race for the prevention of early cartilage injury. The primary outcome of interest was cartilage relaxation time, as measured by T1p and T2 values determined with a high-field quantitative MRI. Follow up occurred about 72 hours and 3 months post-marathon. Results revealed no significant differences in the change from baseline of T1p and T2 relaxation times at all time points in all 8 measured regions of interest between the hyaluronic acid and placebo groups.