The collagenase-induced osteoarthritis (CIOA) model: Where mechanical damage meets inflammation.

Objective: To characterize inflammatory and mechanical changes in the collagenase-induced OA (CIOA) model in rats.

Design: Skeletally mature, 6-month-old Wistar rats received unilateral intraarticular injections of saline, 500 U or 1000 U of collagenase on days 0 and 2 of the study. Joint tissues were harvested on either day 4 or 70 to evaluate the acute and long-term changes.