Weight-bearing asymmetry and vertical activity differences in a rat model of post-traumatic knee osteoarthritis

Abstract

This study used a rat model of post-traumatic knee osteoarthritis (OA) created by anterior cruciate ligament transection with partial medial meniscectomy (ACLT+pMMx). In this model, mild to moderate structural changes that are typical of knee OA have been observed within 2 and 8weeks post-surgery. We aimed to determine whether pain-related behaviours can distinguish between an ACLT+pMMx and a sham surgery group. Three-month old male Sprague-Dawley rats underwent ACLT+pMMx on their right hindlimb within two groups of n=6 each, and sham surgery within two groups of n=5 each. Assessments evaluated percent ipsilateral weight-bearing for static weight-bearing and 18 different variables of exploratory motor behaviour at multiple time points between 1 and 8weeks post-surgery. Histology was performed on the right hindlimbs at 4 and 8weeks post-surgery. Histology confirmed mild to moderate knee OA changes in the ACLT+pMMx group and the absence of knee OA changes in the sham group. Compared to the sham group, the ACLT+pMMx group had significantly lower percent ipsilateral weight-bearing from 1 through 8weeks post-surgery. Compared to the sham group, the ACLT+pMMx group had significantly lower vertical activity (episode count, time, and count) values. These findings suggest that ipsilateral weight-bearing deficit and vertical activity limitations resulted from the presence of knee OA-like changes in this model. When using the ACLT+pMMx-induced rat model of knee OA, percent ipsilateral weight-bearing and vertical activity distinguished between rats with and without knee OA changes. These variables may be useful outcome measures in preclinical research performed with this experimental post-traumatic knee OA model.