Although postural instability is one of the major symptoms of Parkinson's disease (PD), dopaminergic treatment is ineffective for treating postural instability. Recent reports have shown that somatosensory deficit is associated with postural instability, and that somatosensory input improved postural instability. The purpose of this study is to evaluate the effects of lateral wedges for quiet standing postural control in people with PD.

Twenty-two patients who were diagnosed with PD were enrolled in this study. The participants stood on a force plate under two conditions (wedge and no wedge) with or without having their eyes open or closed. The center of pressure (COP) range and velocity were analyzed using a two-way repeated-measures analysis of variance.

The range and velocity of COP in the anterioposterior and mediolateral (ML) directions were significantly improved after the patients stood on the lateral wedge with their eyes closed ( p < 0.05). The range in ML direction and velocity in both directions of COP were significantly decreased when their eyes were open ( p < 0.05).

Regardless of vision, standing on lateral wedges improved postural sway in people with PD.