Figure 5: Quantitative Histological Scores.

The cartilage lesion, osteochondral interface, growth plate, osteophyte (when present), and medial joint capsule were traced in GEKO, with histological scores calculated from these traces. Cartilage parameters are shown in Row 1 & 2. Relative to contralateral and skin-incision controls, MCLT+MMT operated knees had decreased cartilage area, more cartilage damage, larger total degeneration widths (which includes proteoglycan loss), and larger cartilage matrix loss widths (which does not include proteoglycan loss). Bone and synovial changes are shown in Row 3 & 4. Here, MCLT+MMT operated knees had larger osteophytes, more ossification of the hypertrophic cartilage, and larger tibial plateau widths relative to contralateral and skin-incision controls. Finally, the medial joint capsule width in MCLT+MMT operated knees was wider relative to its contralateral control. Age significantly affected measures of cartilage damage. Histological data demonstrate that, relative to 3 month old animals, 6 month and 9 month old animals had decreased cartilage area, larger total cartilage degeneration widths, and more evidence of hypertrophic cartilage damage. Cartilage damage (lesion size) was also larger in 9 month old animals relative to 3 month old animals. Relevant ANOVA main effect and interaction p-values are provided in Supplemental Table 1.