Evaluation of Agreement Between Numerical Rating Scales, Visual Analogue Scoring Scales, and Force Plate Gait Analysis in Dogs MARGARET M. QUINN, BS, NICHOLAS S. KEULER, MS, YAN LU, MD, MARIA L. E. FARIA, DVM, PhD, PETER MUIR, BVSc, MVetClinStud, PhD, Diplomate ACVS, and MARK D. MARKEL, DVM, PhD, Diplomate ACVS Objective—To evaluate the accuracy of numerical rating (NRS) and visual analogue (VAS) scoring scales compared with force plate gait analysis and agreement between observers for each scoring scale. Study Design—Experimental study. Animals—Mixed breed dogs (n ¼ 21) with a right limb tibial osteotomy repaired with an external fixator. Methods—Three small-animal veterinarians with orthopedic training scored lameness using NRS and VAS before surgery, and at 4 and 8 weeks after surgery. Peak force and impulse were de- termined at the same time points using a force plate. Agreement between observers and with force plate data was assessed. Significance was set at P  .05. Results—Agreement was generally low among observers for both NRS and VAS scores. When evaluated at each time point, an acceptable level of agreement was present only at 4 weeks after surgery. Only impulse had a significant relationship with some of the observers’ subjective scores. No significant relationships between any observer’s scores and force plate data existed if very lame dogs were omitted. Conclusions—Subjective scoring scales do not replace force plate gait analysis. Agreement is low unless lameness is severe, and each observer uses an individually unique scale. Subjective scoring scales most accurately reflect force plate gait analysis when lameness is severe. Clinical Relevance—Subjective lameness scoring scales may not accurately reflect lameness and do not replace force plate gait analysis. Observers must stay the same during the duration of a study for accurate analyses. r Copyright 2007 by The American College of Veterinary Surgeons INTRODUCTION F ORCE PLATE gait analysis has become an accepted technique for accurate and objective evaluation of limb function in humans and animals. 1,2 Lameness or impaired limb function caused by trauma, disease and pain is manifested by a wide range of clinical signs from slight unnoticeable gait changes to complete avoidance of the lame limb. Force plate gait analysis can be used as a tool to deduce pain, disease, and healing. 3–5 Additionally, numerical rating scales (NRS) and visual analogue scales (VAS) have been used to subjectively evaluate limb func- tion. 6–8 Subjective scoring systems may be useful in clin- ical and research evaluation of gait where obtaining and maintaining a force plate cannot be afforded, such as a private clinical practice. With a force plate, measures of the forces exerted by a dog’s limb on the ground during ambulation can be made. Peak force (maximal force applied during stance phase) and impulse (total force applied over time) in the vertical axis are the most commonly used variables to assess degree of lameness. 9,10 Precise acquisition of these Address reprint requests to Yan Lu, MD, Comparative Orthopaedic Research Laboratory School of Veterinary Medicine, 2015 Linden Drive, Madison, WI 53706. E-mail: luy@svm.vetmed.wisc.edu. Submitted September 2006; Accepted February 2007 From the Comparative Orthopaedic Research Laboratory, Departments of Medical Sciences and Surgical Sciences, School of Veterinary Medicine and the Department of Statistics, University of Wisconsin-Madison, Madison, WI. r Copyright 2007 by The American College of Veterinary Surgeons 0161-3499/07 doi:10.1111/j.1532-950X.2007.00276.x 360 Veterinary Surgery 36:360–367, 2007