Evaluation of gait symmetry after stroke: A comparison of current methods and recommendations for standardization Kara K. Patterson a,b,1 , William H. Gage b,c,e,2 , Dina Brooks a,b,d,3 , Sandra E. Black a,b,e,f,4 , William E. McIlroy a,b,e,g, * a Graduate Department of Rehabilitation Science, University of Toronto, Toronto, Ontario, Canada b Toronto Rehabilitation Institute, Toronto, Ontario, Canada c School of Kinesiology and Health Science, York University, Toronto, Ontario, Canada d Department of Physical Therapy, University of Toronto, Toronto, Ontario, Canada e Heart and Stroke Foundation Centre for Stroke Recovery, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada f Division of Neurology, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada g Department of Kinesiology, University of Waterloo, Waterloo, Ontario, Canada 1. Introduction Symmetry is an important gait characteristic that is increas- ingly reported, particularly after stroke. As a measure of the parallels between the lower limbs, symmetry can provide insight about the control of walking which may be unique from more conventional measures such as velocity, and may have a role in guiding the clinician’s treatment decisions [1]. In addition, gait symmetry is important clinically since it may be associated with a number of negative consequences such as inefficiency, challenges to balance control, risk of muscuoloskeletal injury to the non- paretic lower limb and loss of bone mass density in the paretic lower limb [1,2]. Despite the potential importance, there is no commonly accepted standard for either the method used to calculate gait symmetry or the gait parameter to assess. The purpose of the present work is to compare the properties of commonly used expressions of gait symmetry with the goal of achieving a recommendation for standardized practice. Note that the current focus is on spatiotemporal characteristics of gait as they have been most commonly used, even though some studies have advocated for the use of kinematic and/or kinetic indices [3,4]. There are two components of a symmetry measure: (1) the equation to calculate symmetry and (2) the spatiotemporal gait parameter used in the equation. There are two types of symmetry equations: (1) a ratio [5–14] and (2) an index or difference Gait & Posture 31 (2010) 241–246 ARTICLE INFO Article history: Received 4 May 2009 Received in revised form 12 October 2009 Accepted 25 October 2009 Keywords: Stroke Gait Symmetry Measurement ABSTRACT Symmetry is a gait characteristic that is increasingly measured and reported, particularly in the stroke patient population. However, there is no accepted standard for assessing symmetry making it difficult to compare across studies and establish criteria to guide clinical decision making. This study compares the most common expressions of spatiotemporal gait symmetry to describe post-stroke gait and makes recommendations regarding the most suitable measure for standardization. The following symmetry equations were compared: symmetry ratio, symmetry index, gait asymmetry and symmetry angle using step length, swing time, stance time, double support time and an intra-limb ratio of swing: stance time. Comparisons were made within a group of 161 community-dwelling, ambulatory individuals with stroke and 81 healthy adults as a reference group. Our analysis supports the recommendations of the symmetry ratio as the equation for standardization and step length, swing time and stance time as the gait parameters to be used in the equation. Future work should focus on establishing the intra-individual variability of these measures and linking them to mechanisms of gait dysfunction. ß 2009 Elsevier B.V. All rights reserved. * Corresponding author at: Department of Kinesiology, University of Waterloo, 200 University Avenue West, Waterloo, ON, Canada N2L 3G1. Tel.: +1 519 888 4567x38109. E-mail addresses: kara.patterson@utoronto.ca (K.K. Patterson), whgage@yorku.ca (W.H. Gage), dina.brooks@utoronto.ca (D. Brooks), sandra.black@sunnybrook.ca (S.E. Black), wmcilroy@uwaterloo.ca (W.E. McIlroy). 1 Jewish Rehabilitation Hospital, Feil & Oberfeld Research Centre, 3205 Alton Goldblom Place, Laval, QC, Canada H7V 1R2. Tel.: +1 450 688 9550x4817; fax: +1 450 688 3673. 2 School of Kinesiology and Health Science, York University, Bethune College, 4700 Keele Street, Toronto, ON, Canada M3J 1P3. Tel: +1 416 736 5728x33027. 3 Department of Physical Therapy, University of Toronto, 500 University Ave, Toronto, ON, Canada M5G 1V7. Tel.: +1 416 978 1739. 4 Heart and Stroke Foundation Centre for Stroke Recovery, Sunnybrook Health Sciences Centre, 2075 Bayview Ave, Toronto, ON, Canada M4N 3M5. Tel.: +1 416 480 4551. Contents lists available at ScienceDirect Gait & Posture journal homepage: www.elsevier.com/locate/gaitpost 0966-6362/$ – see front matter ß 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.gaitpost.2009.10.014