Histopathological scoring. Histopathological assessment of cartilage degenerative changes in the medial tibial plateau (MTP) of control animals and animals injected with 250 or 500 U collagenase, one, two, four and six weeks after injection. The following parameters were evaluated: cartilage matrix loss width (CMLW) measured along the surface (0% depth, A), the midzone (50% depth, B) and tidemark (100% depth, C); total cartilage degeneration width (TCDW, D); significant cartilage degeneration width (SCDW, E); osteophyte score (OS, F); zonal depth ratio (ZDR) of lesions at zone 1 (at the medial edge of the joint, G), zone 2 (at the centre of the MTP, H) and zone 3 (adjacent to the cruciate ligaments, I); cartilage degeneration score (CDS) at zones 1 (J), 2 (K) and 3 (L); synovial membrane inflammation score (SMIS, M); medial joint capsule width (MJCW, N); growth plate thickness (GPT, O). Mean ± SEM. Measured parameters were analysed by one-way ANOVA followed by Tukey post-hoc test; scored parameters were analysed by the Kruskal-Wallis test with Dunn’s post-hoc test. *P <0.05, **P <0.01, ***P <0.001, for comparisons between collagenase injected and control animals within each time point; +P <0.05, +++P <0.001, for comparisons between the 250 and 500 U groups within each time-point; #P <0.05, ###P <0.001, for comparisons between week 1 and week 6 within each group; ‡P <0.05, ‡‡P <0.01, ‡‡‡P <0.001, for comparisons between week 2 and week 6 within each group; †P <0.05, ††P <0.01, †††P <0.001, for comparisons between week 4 and week 6 within each group; ¥P <0.05, ¥¥P <0.01, ¥¥¥P <0.001, between collagenase injected and control animals from a different time point.