Cartilage quality and quantity was determined from samples of sedentary (round boxes) and running (square boxes) rats with equilibrium partitioning of a ionic contrast agent by using (EPIC-)μCT (A-D). The amount of sulfated-glycosaminoglycans (sGAGs) (arbitrary gray values; A, B) and cartilage thickness (μm; C, D) were measured of medial (A,C) and lateral (B,D) cartilage compartments of the tibial plateau harvested from control (blank boxes) and sGAG depleted joints (gray boxes). Attenuation values from EPIC-μCT scans are inversely related to the sGAG content, meaning that a high attenuation corresponds to low sGAG content. Coronal images from representative EPIC-μCT scans of the tibial plateau show the amount of cartilage (erosions indicated with ▼ and dashed lines) and sGAG content (displayed in color) (E). * < 0.05, **P < 0.01, ***P < 0.001; error bars indicate 95% confidence intervals.