Postural stability during the transition from double-leg stance to single-leg stance in anterior cruciate ligament injured subjects Bart Dingenen a, ⁎, Luc Janssens b,c , Thomas Luyckx d , Steven Claes d,e , Johan Bellemans d , Filip F. Staes a a KU Leuven, Musculoskeletal Rehabilitation Research Group, Department of Rehabilitation Sciences, Faculty of Kinesiology and Rehabilitation Sciences, Tervuursevest 101 b1501, 3001 Heverlee, Belgium b KU Leuven, Department of Electrical Engineering, Faculty of Engineering Technology Services, Andreas Vesaliusstraat 13, 3000 Leuven, Belgium c KU Leuven, Cardiovascular and Respiratory Rehabilitation Research Group, Department of Rehabilitation Sciences, Faculty of Kinesiology and Rehabilitation Sciences, Tervuursevest 101 b1501, 3001 Heverlee, Belgium d Department of Orthopedics, University Hospitals Leuven, Campus Pellenberg, Weligerveld 1, 3212 Pellenberg, Belgium e Department of Orthopedic Surgery, AZ Herentals Hospital, Nederrij 133, 2200 Herentals, Belgium abstract article info Article history: Received 1 December 2014 Accepted 9 January 2015 Keywords: Anterior cruciate ligament injury Postural stability Balance Double-leg stance Single-leg stance Background: An anterior cruciate ligament injury may lead to deteriorations in postural stability. The goal of this study was to evaluate postural stability during the transition from double-leg stance to single-leg stance of both legs in anterior cruciate ligament injured subjects and non-injured control subjects with a standardized methodology. Methods: Fifteen control subjects and 15 anterior cruciate ligament injured subjects (time after injury: mean (SD) = 1.4 (0.7) months) participated in the study. Both groups were similar for age, gender, height, weight and body mass index. Spatiotemporal center of pressure outcomes of both legs of each subject were measured during the transition from double-leg stance to single-leg stance in eyes open and eyes closed conditions. Movement speed was standardized. Findings: The center of pressure displacement after a new stability point was reached during the single-leg stance phase was significantly increased in the anterior cruciate ligament injured group compared to the control group in the eyes closed condition (P b .001). No significant different postural stability outcomes were found between both legs within both groups (P N .05). No significant differences were found during the transition itself (P N .05). Interpretation: The anterior cruciate ligament injured group showed postural stability deficits during the single- leg stance phase compared to the non-injured control group in the eyes closed condition. Using the non-injured leg as a normal reference when evaluating postural stability of the injured leg may lead to misinterpretations, as no significant differences were found between the injured and non-injured leg of the anterior cruciate ligament injured group. © 2015 Elsevier Ltd. All rights reserved. 1. Introduction Anterior cruciate ligament (ACL) tears are serious injuries with substantial short- and long-term consequences, even when ACL reconstruction is performed (Ardern et al., 2014; Wright et al., 2011). Studying postural stability in ACL injured (ACLI) subjects has become prevalent in literature (Ageberg et al., 2001; Bonfim et al., 2008; Gauffin et al., 1990; Lysholm et al., 1998; Negahban et al., 2009; Okuda et al., 2005; Zatterstrom et al., 1994), as these measurements may provide insights in the complex body's adaptation mechanisms after injury. In fact, the ACL is more than just a mechanical constraint of the knee joint. Proprioceptive deficits have been shown in ACLI subjects (Barrack et al., 1989; Corrigan et al., 1992). This altered afferent information may lead to adaptations in the organization of the central nervous system (CNS) (Kapreli et al., 2009), which may provide a possi- ble explanation for the findings of a recent systematic review whereby it was concluded that postural stability is impaired not only in the injured leg, both also in the non-injured leg after ACL injury (Negahban et al., 2013). However, because of the heterogeneity in outcome measure- ments within the included studies, it was not possible to conduct a meta-analysis. Most of the previous studies focused on a single-leg stance task while standing on a fixed force plate to measure postural stability in ACLI subjects (Ageberg et al., 2001; Bonfim et al., 2008; Gauffin et al., 1990; Lysholm et al., 1998; Negahban et al., 2009; Okuda et al., 2005; Zatterstrom et al., 1994). Before a person is standing on one leg, weight needs to be shifted from a relatively stable double-leg stance position towards a smaller base of support during single-leg stance. Subjects with pathology tend to perform this transitional Clinical Biomechanics xxx (2015) xxx–xxx ⁎ Corresponding author. E-mail addresses: bart.dingenen@faber.kuleuven.be (B. Dingenen), luc.janssens@kuleuven.be (L. Janssens), luyckx.thomas@gmail.com (T. Luyckx), steven@kreutzfeldverein.be (S. Claes), johan.bellemans@skynet.be (J. Bellemans), filip.staes@faber.kuleuven.be (F.F. Staes). JCLB-03899; No of Pages 7 http://dx.doi.org/10.1016/j.clinbiomech.2015.01.002 0268-0033/© 2015 Elsevier Ltd. All rights reserved. Contents lists available at ScienceDirect Clinical Biomechanics journal homepage: www.elsevier.com/locate/clinbiomech Please cite this article as: Dingenen, B., et al., Postural stability during the transition from double-leg stance to single-leg stance in anterior cruciate ligament injured subjects, Clin. Biomech. (2015), http://dx.doi.org/10.1016/j.clinbiomech.2015.01.002