Gait symmetry measures: A review of current and prospective methods

Gait symmetry is important in measuring gait pattern alterations for establishing the level of functional limitation due to pathology, observing its changes over time and evaluating rehabilitative intervention effects. The aim of this topical review is twofold: 1) to present used symmetry measures and summarize their application to a diverse range of gait data and to demonstrate their capabilities in their utilization in research and practice, 2) to expose newly developed symmetry measures and highlight their perspectives. We divided symmetry measures into four subgroups: symmetry indices, complete gait cycle symmetry measures, statistically-based measures and approaches, and nonlinear measures. For each, we will discuss their advantages and limitations and raise new questions and recommendations about their development and clinical use.