Quantitative Gait Analysis Detects Significant Differences in Movement between Osteoarthritic and Nonosteoarthritic Guinea Pig Strains before and after Treatment with Flunixin Meglumine

A computer-aided gait analysis system was used to contrast two guinea pig strains with differing propensity for osteoarthritis (OA), with/without administration of a nonsteroidal anti-inflammatory drug. Walking speed and static/dynamic gait parameters were determined at baseline. Flunixin meglumine was given and animals were evaluated 4, 24, and 72 hours after treatment. Body weight was compared using unpaired -tests. Knee joints were histologically evaluated using species-specific criteria; indices were analyzed using one-way ANOVA, Kruskal-Wallis test, followed by Dunn’s multiple comparisons. A generalized linear model followed by Tukey’s posttests juxtaposed gait parameters; walking speed was a covariate for other outcome measures. Body weight was not different between strains; OA-prone animals demonstrated more progressive chondropathy. At baseline, OA-prone animals had slower walking speeds, narrower hind limb bases of support, shorter stride lengths, and slower limb swing speeds relative to OA-resistant animals. These differences were not detected 4 or 24 hours after treatment. By 72 hours, OA-prone animals had returned to baseline values. These findings indicate a distinct voluntary gait pattern in a rodent model of bilateral primary OA, modification of which may allow rapid screening of novel therapies. Flunixin meglumine temporarily permitted OA-prone animals to move in a manner that was analogous to OA-resistant animals. 1. Introduction The major clinical symptom associated with osteoarthritis (OA) is pain during motion. Unfortunately, the severity of joint disease determined via imaging and histology is often only weakly associated with the chief complaint [1]. As disturbances in movement are known consequences of pain [2], analyses of gait in parallel with standard measures of pathology have started to find favor with animal models of human disease. Techniques utilized to evaluate OA in rodents include assessment of musculoskeletal function (grip strength meters, rotarod testing) and gait and spontaneous activity testing (force platforms, video-recorded open-field and arena trials) [3]. Walkway- [4] and treadmill-associated [5] computer-aided gait analysis systems have also been validated to gauge gait abnormalities in injury-induced models of arthritis. An automated quantitative gait analysis method, the Noldus CatWalk, determines a large number of locomotion parameters in laboratory animals during spontaneous, unforced platform crossing [6]. This computer-assisted method objectively and rapidly monitors a large number of both dynamic and