Fig. 1.

Shows the pain behaviour and knee histology in early phase (EP) and late phase (LP) MIA animals. Scale bars = 500 μM. A) early inflammatory phase (EP) MIA animals place less weight on the injured limb than sham controls (EP n = 15, early phase sham (EPS) n = 12). B) late chronic phases (LP) MIA animals place significantly less weight on the injured limb than sham controls at all time points tested (LP n = 14, late phase sham (LPS) n = 14). C) EP MIA animals have a reduced paw threshold compared to sham controls (EP n = 10, EPS n = 10). D) LP MIA animals have a significantly reduced paw withdrawal threshold than sham controls at all time points tested (LP n = 10, LPS n = 13). E) EP MIA animals display very little cartilage degradation. F) LP MIA animals display extensive cartilage damage. G-H) EP and LP sham animals display no cartilage degradation H) For maximum knee histology score, LP MIA animals have a significantly higher knee histology score than their respective sham control group, while EP MIA animals have similar knee histology scores to their respective sham control group (EP n = 6, EPS n = 6, LP n = 9, LPS n = 5). I) For average knee histology score LP MIA animals have a significantly higher knee histology score than their respective sham control group, but EP MIA animals do not have a significantly higher average knee score than sham controls (EP n = 6, EPS n = 6, LP n = 9, LPS n = 5). J) There is a significant negative linear relationship between average knee histology score and the weight placed on the injured limb in LP MIA animals (n = 9). There is a negative linear relationship between knee histology score and paw withdrawal threshold or weight placed on the injured limb in LP animals (n = 9). (A–H: Kruskall–Wallis. K–L: Linear regression analysis, R² = strength of relationship and P value calculated from F-test of overall significance. *P < 0.05, **P < 0.01). EP = EP MIA, EPS = EP sham, LP = LP MIA, LPS = LP sham.