Gait Symmetry and Its Evaluation Methods: A Review

Due to the fact that walking is the main activity of humans to relocate, understanding its complexity and its different angles has long been the focus of various studies. One of the main issues in this regard is gait symmetry. Accordingly, the aim of the present study was investigating the concept of gait symmetry and the methods for evaluating it.
A search among the related articles published from 2000 to 2015 in valid scientific databases, according to the research criteria, resulted in 71 scientific articles selected for the present review study.
Review of the previous studies showed that generally, from kinematical and kinetical point of view, walking in participants with and without abnormalities was asymmetrical and this condition is represented in all measured kinematic and kinetic parameters except in a few studies. Also, the methods of evaluating gait symmetry could generally be categorized into symmetry indices and statistical methods. In this situation, symmetry indices, despite their ease of application, could not represent the spatial-time complexity of walking cycle because of single-variable evaluations. In addition, the main limitation of statistical methods is that they do not present a qualitative value. Thus, for neither of these two methods is normal data available.
With respect to the fact that during walking lower limbs have an asymmetrical behavior in normal/healthy individuals, which is due to their different functional tasks in control and propulsion, the assumption of gaining perfect symmetry after rehabilitation and intervention does not seems to be true. However, it is crucial to carry out further investigations in order to obtain the normal range of gait asymmetry in different participants and to understand fundamental factors affecting gait asymmetry.