The retropulsion test: a good evaluation of postural instability in Parkinson's disease?

Postural instability is a disabling feature of Parkinson's disease (PD), contributing to recurrent falls and fall-related injuries. The retropulsion test is widely regarded as the gold standard to evaluate postural instability, and is therefore a key component of the neurological examination in PD. Many variants exist, which confuses both clinical practice and research. Here, we evaluate the merits of this test by discussing three common variants: (1) the pull test as described in the MDS-UPDRS scale; (2) using an unexpected shoulder pull, without prior warning; and (3) the push-and-release test. All variants are a quick method to index the degree of postural instability, but the outcome can vary considerably due to variability in test execution and -interpretation. This partially explains why the retropulsion test fails to predict future falls in PD. Another explanation is that falling results from the complex interplay between gait, balance, cognitive decline and environmental factors, and the retropulsion test captures only part of that. We conclude with several recommendations for current clinical practice.