Turning problems and freezing of gait in Parkinson's disease: a systematic review and meta-analysis.

To understand the differences of step and turn parameters between freezers and non-freezers during turning and determine the influence of turn angle and turn characteristics on freezing of gait. PubMed and Web of Science were searched from the earliest data available to August 2017. Case-control studies that examined the differences in turning while walking between freezers and non-freezers were included.