Review Bilateral balance impairments after lateral ankle trauma: A systematic review and meta-analysis Erik A. Wikstrom a, *, Sagar Naik b , Neha Lodha b , James H. Cauraugh b a Biodynamics Research Laboratory, Kinesiology Department, University of North Carolina at Charlotte, 9201 University City Blvd, Charlotte, NC 28223, United States b Applied Physiology and Kinesiology Department, University of Florida, United States Lateral ankle sprains are a common consequence of physical activity and sports performance, and frequently residual symp- toms arise (e.g. ligamentous laxity, impaired postural control and complaints of the ankle giving way) [1]. Indeed, up to 74% of the individuals who suffer an acute lateral ankle sprain develop residual symptoms defined as chronic ankle instability (CAI) [2]. Unfortunately, the underlying neurophysiological mechanism for CAI remains unclear; however, evidence suggests that both feedback and feed-forward alterations in neuromuscular control may play a role in developing CAI [3,4]. A neurophysiological marker of centrally mediated changes, such as feed-forward alterations, is the presence of bilateral postural control impairments. Specifically, bilateral postural control impairments involve measuring postural control during a single leg stance on both a patient’s involved and uninvolved limb and then comparing the values to performances by a healthy control group. Two recent publications provided robust evidence associating an acute lateral ankle sprain with impaired postural control in the involved limb [5,6]. In addition, three recent meta- analyses revealed convincing evidence that postural control is impaired in the involved limb of patients with CAI [6–8]. Moreover, while formulating the discussion of their meta-analysis Wikstrom et al. [6] indicated that bilateral balance deficits were a viable explanation for the lack of significant findings between the involved and uninvolved limbs in previous investigations. Based on the above converging arguments, we asked an important research question: are postural control impairments of the uninvolved limb a function of acute ankle injury or CAI? to answer this question we conducted separate meta-analyses on existing postural control assessments of the involved and uninvolved limbs relative to an uninjured control group. Providing systematic evidence of the presence of bilateral postural control deficits is fundamentally attractive because health care providers frequently use the uninjured limb as a criterion for normal postural control. However, if bilateral balance deficits exist, then using the uninvolved limb may lead to inappropriate conclusions and a hasty return to activity [6]. Thus, quantitatively determining standar- dized effect sizes will provide empirical evidence regarding the Gait & Posture 31 (2010) 407–414 ARTICLE INFO Article history: Received 6 March 2009 Received in revised form 9 December 2009 Accepted 5 February 2010 Keywords: Ankle sprain Chronic ankle instability Bilateral postural control Systematic review ABSTRACT Research indicates that balance is impaired in the involved limb following an ankle injury. However, bilateral balance impairments are a viable reason for previous non-significant findings between involved and uninvolved limbs. The purpose of this investigation was to conduct a meta-analysis on studies reporting the effects of lateral ankle trauma on balance of the involved and uninvolved limb after acute ankle injury and chronic ankle instability. Twelve studies qualified for inclusion and assessed static balance for both the involved and uninvolved limbs post-injury and a control group. Meta-analyses calculated standardized mean difference effects and explored moderating variables for the involved and uninvolved limbs relative to controls. A significant cumulative effect size (ES = 0.448, p < 0.00001) indicated that balance of the involved limb is impaired after a history of ankle injury. Moderator variable analysis revealed that both acute (ES = 0.529, p < 0.0002) and chronic (ES = 0.338, p < 0.001) lateral ankle trauma negatively affected balance. Analysis of the uninvolved limb also revealed postural stability impairments (ES = 0.275, p < 0.003). Additional, moderator analysis showed a significant acute effect (ES = 0.564, p < 0.0001), but failed to find significance for individuals with chronic ankle instability (ES = 0.070, p = 0.552). These findings provide strong evidence that balance is bilaterally impaired after an acute lateral ankle sprain. However, these findings suggest that bilateral balance deficits are not present in patients with chronic ankle instability. Based on these findings, the uninvolved limb should not be used as a reference for ‘‘normal balance’’ following an acute lateral ankle sprain. Further, patients with acute lateral ankle sprains should undergo balance training on both limbs. ß 2010 Elsevier B.V. All rights reserved. * Corresponding author. Tel.: +1 704 687 3764; fax: +1 704 687 3350. E-mail address: ewikstrom@uncc.edu (E.A. Wikstrom). Contents lists available at ScienceDirect Gait & Posture journal homepage: www.elsevier.com/locate/gaitpost 0966-6362/$ – see front matter ß 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.gaitpost.2010.02.004