Inflammation index. Joint swelling assessed by measuring knee diameters (difference between ipsilateral and contralateral knees). Collagenase-injected animals present increased knee diameters one week after injection. The number of animals per group at each time-point is indicated below the graphs. An initial number of 24 animals was used in each group. Animals were then sacrificed at different time-points for histopathology (one, two, four and six weeks; n = 6 per dose and per time-point). Mean ± SEM, two-way ANOVA followed by Bonferroni post-hoc test for comparisons between groups at each time-point. ***P <0.001, for comparisons between control and the 500 U collagenase group.