Thinning of cartilage associated with reduced weight bearing and/or low-dose irradiation vs. ground-sham is localized to the anatomic point of greatest load-bearing in the medial tibial plateau, specifically the tibial-femoral cartilage-cartilage contact point (graph, upper right; arrow indicates spatial location in contrast-enhanced microCT image of knee cartilage in cross section) compared using two-way ANOVA, with P values from Tukey’s post hoc analysis presented (*P < 0.05, **P < 0.01, ***P < 0.001). Other than treatments vs. ground-sham, no inter-group comparisons showed significant differences.