Evaluation of Osteoarthritis in Cats: Novel Information from a Pilot Study Martin Guillot 1 , DV, MSc, Maxim Moreau 1 , MSc, Marc-Andr ´ e d’Anjou 1 , DMV, DACVR, Johanne Martel-Pelletier 2 , PhD, Jean-Pierre Pelletier 2 , MD, and Eric Troncy 1,2 , DV, PhD, DUn 1 Groupe de Recherche en Pharmacologie Animale du Qu´ ebec (GREPAQ) and the Companion Animal Research Group, Facult´ e de M ´ edecine V´ et ´ erinaire, Universit ´ e de Montr ´ eal, Saint-Hyacinthe, Qu ´ ebec Canada and 2 Osteoarthritis Research Unit, Centre hospitalier de l’Universit´ e de Montr ´ eal, H ˆ opital Notre-Dame, Montr ´ eal, Qu ´ ebec, Canada Corresponding Author Eric Troncy, DV, PhD, DUn, Osteoarthritis Research Unit, Centre hospitalier de l’Universit ´ e de Montr ´ eal (CRCHUM), Notre-Dame Hospital, 1560 Sherbrooke Street East, Pavillon J.-A. de S` eve, Office Y-2606, Montr ´ eal (QC), H2L 4M1 Canada E-mail: eric.troncy@umontreal.ca Submitted November 2010 Accepted January 2012 DOI:10.1111/j.1532-950X.2012.00976.x Objective: To describe structural changes associated with osteoarthritis (OA) in cats and to quantify OA-associated disability using functional evaluations. Study Design: Cross-sectional pilot study with longitudinal data. Animals: Normal cats (n = 2) and coxofemoral joint OA cats (n = 4) were evaluated by physical examination, radiography, and magnetic resonance imaging (MRI). Methods: Structural changes related to OA were scored using computed radio- graphs (CR) and MRI. Functional evaluation consisted of podobarometric gait analyses performed using a pressure-sensitive mattress and motor activity assess- ments using collar-attached, accelerometer-based activity sensors. Results: Structural scores for the coxofemoral joint OA-related lesions were lower in normal cats than OA cats for MRI (P = .07). Use of MRI allowed for whole- organ assessment of the coxofemoral joint. Pelvic limb peak vertical ground reac- tion force (PVF) was higher in normal cats than OA cats (P = .10). During the night, motor activity was greater in normal cats than OA cats (P = .04). PVF was positively correlated with mean motor activity (Spearman coefficient [Rho] = 0.83, P = .04) and negatively correlated with age and MRI structural score (Rho =−0.93 and −0.79, P < .01 and .06, respectively). Conclusions: This study provides the first description of OA-related lesions in cats using MRI. Gait analysis and accelerometry should be considered as objective tools to characterize OA-associated disability, although these assessments were weakly correlated with structural changes. Osteoarthritis (OA) is the most common disabling condi- tion of dogs and cats in North America. 1 Complex me- chanical and biological processes lead to articular tissue degeneration characterized by cartilage degradation, sub- chondral bone marrow lesions, synovial inflammation, and chronic pain. 2, 3 In cats, OA more frequently affects elbow, coxofemoral, and stifle joints, and its prevalence increases dramatically with age. 4–8 In dogs, horses, and people, mag- netic resonance imaging (MRI) is more sensitive than ra- diography for assessing OA structural changes, and MRI provides better definition for observing major OA-related changes (cartilage lesions, osteophytosis, joint effusion, and Study conducted at GREPAQ, Department of Veterinary Biomedical Sciences, Facult ´ e de M ´ edecine V ´ et ´ erinaire, Univer- sit ´ e de Montr ´ eal, in collaboration with the CRCHUM, Universit ´ e de Montr ´ eal and ArthroLab, Inc., Montr ´ eal, Qu ´ ebec, Canada. Presented in part at the Pain and Pain Management in Non- Human Species Special Interest Group Official Satellite Sym- posium of the 13th World Congress on Pain, Montreal, Canada (August 29, 2010). synovial thickening). 9–11 MRI can also be used to reliably assess progression of OA and should be increasingly used in animals to assess the effects of disease-modifying OA drugs (DMOADs). 12, 13 We are unaware of MRI descriptions of coxofemoral joint OA lesions in cats or their relationship with radiographic findings. In cats, joint pain leads to decreased daily activity, a reluctance to jump, and other altered behaviors, such as dif- ficulty finding a comfortable position, grooming, and play- ing, which can be detected by owners. 1, 14, 15 However, OA is less frequently reported in cats, possibly because of the poor behavioral expression of pain in cats or to the paucity of documented correlations between orthopedic evaluation and severity of the OA structural changes. 8, 16, 17 Moreover, this could also be because of inadequate pain assessment in cats because of a lack of validated, precise, and sen- sitive techniques to measure clinical outcomes. 8, 17–19 Un- fortunately, this has led to an absence of medications ap- proved for the treatment of pain-related OA in cats in North America. In addition, species-specific differences in pain 328 Veterinary Surgery 41 (2012) 328–335 C  Copyright 2012 by The American College of Veterinary Surgeons