Forced mobilization apparatus and macroscopic analysis of joint degradation. (a) Following sham (control) or OA surgery, FM animals underwent forced mobilization. Animals walked on a rotating cylinder for 30 min, three times per week. (b) FM forces the maximal extension and flexion of the knee joint (white arrow). To assess macroscopic changes to the articular surface, knee joints were dissected 4 weeks after surgery and photographed. Representative images from sham (c) tibias and (d) femurs, and ipsilateral (e) tibias and (f) femurs are shown. Surface abrasions (black arrow) and fibrotic tissue (arrow head) were observed in ipsilateral surfaces, compared with the smooth, glassy appearance in shams. Scale bar applies to panels c-f. FM, forced mobilization; OA, osteoarthritis.