We introduce a method to reliably determine changes in healthy knee cartilage composition after joint loading. Ten healthy participants were imaged before and after participant repositioning to determine the test-retest repeatability of T1ρ and T2 relaxation time mapping. Additionally, nine healthy participants were imaged before and after a mild, dynamic stepping exercise. Three-dimensional surface analysis of patellar, femoral, and lateral and medial tibial cartilage was performed. The exercise surface data was thresholded with the determined measurement errors from the T1ρ and T2 repeatability data to highlight cartilage regions experiencing reliable exercise-induced compositional changes.