Sodium imaging is quantitative technique sensitive to changes in cartilage glycosaminoglycan content. Changes in cartilage matrix, due to maturation or degeneration, may influence sodium relaxation times which can lead to incorrect sodium concentration estimates when not addressed. This ex vivo study employs pediatric knee specimens to evaluate the relationship between sodium relaxation parameters and compositional changes in the developing cartilage matrix. Our preliminary evaluation suggests that cartilage maturation is accompanied by a decrease in sodium T1 and the short T2* component. Sodium concentrations in studies comparing healthy, diseased or immature cartilage should be corrected for possible changes in relaxation times.