Gait kinematics changes in post traumatic knee osteoarthritis with destabilized medial meniscus in rat

Purpose: Mechanical stress is important for osteoarthritis (OA) so that gait analysis is often performed for OA patients, who frequently ambulate with the abnormal joint motion to avoid pain. But the gait kinematics in the rodent OA model is not full elucidated. The objective of this study was to describe kinematic changes of gait in the rat knee OA model with destabilized medial meniscus (DMM) by comparing with sham surgery and naïve control. Methods: Experimental animals were eighteen of 12-week-old male Wister rats, and they were divided into three groups, which are DMM, sham and naïve control group (each n = 6). DMM was performed by the medial meniscotibial ligament transection on the right knee under general anesthesia. Sham rats were received only a capsule incision on the right knee joint. Gait analysis was performed for all rats at 2, 4 and 8 weeks after surgery, using 3D motion capture system (KinemaTracer; KISSEI COMTEC). Measurement parameters were knee range of motion (ROM) and knee angular acceleration, toe-out angle, step distance, stance time. Rats were euthanized just after gait analysis at 8 weeks, then right knee were collected to assess the OA development in histology. The OA development was assessed by OARSI score. Results: There were no significant differences in stance time and step length among groups. Knee flexion angle on Foot Contact (FC) and max knee flexion angle in DMM significantly increased relative to naïve control in 2 and 4 weeks, however there were no difference in 8 weeks (Figure 1). Knee flexion angle in sham was smaller than DMM, but there was only significant difference in 2 weeks between DMM and sham. Max knee flexion angular acceleration in DMM and Sham significantly decreased relative to naïve control in 2 weeks. Max toe-out angle in DMM and sham tended to be smaller than naïve control (Figure 2). Moderate cartilage damage of medial tibiofemoral joint was confirmed in the DMM group by histology, there were significant differences in OARSI score between DMM and other groups (Score ± SD is 13.00 ± 1.00, 1.33 ± 0.52, 0.50 ± 0.55 in DMM, Sham, naïve control respectively) (Figure 3). Conclusions: These data indicate that knee flexion kinematics in DMM and sham significantly changed relative to naïve control until 4 weeks, so that not only the medial meniscus instability but also the capsule incision affected gait kinematics in the early postoperative days. In addition, the relationship between moderate TF cartilage damage and knee flexion kinematics of gait in DMM rats may be weak because there was no difference in the knee flexion kinematics in 8 weeks.