Does foot morphology influences postural control in people with multiple sclerosis?

Postural instability is a common impairment in people with Multiple Sclerosis (pwMS) and is primarily attributed to delayed somatosensory conduction and deficits in central sensory integration. However, the full range of factors contributing to dysfunctions in the postural control system remains partly unclear. This study aimed to investigate the role of the foot-ground interface-closely associated with foot morphology, particularly the height of the medial longitudinal arch-in modulating postural stability. To this end, 94 pwMS (mean age: 47.5 years; mean Expanded Disability Status Scale score: 3.3) underwent concurrent assessments of postural sway and plantar pressure distribution using a pressure platform, during quiet upright stance performed under both eyes-open and eyes-closed conditions. Postural sway was quantified through analysis of the center of pressure (COP) time series, and foot morphology was classified as high, normal, or low arch according to cut-off values of the Arch Index (AI), a parameter calculated on the basis of the regional contact area at forefoot, midfoot and rearfoot. Results revealed that, only in the absence of visual input, pwMS with high-arched feet-and to a lesser extent those with low arches-demonstrated significantly increased postural sway compared to those with normal arches, as indicated by larger sway areas, greater COP path lengths, and increased maximum COP displacements in anteroposterior and mediolateral directions. These findings suggest that foot morphology may serve as a relevant factor in identifying pwMS at elevated risk of balance impairments and falls, supporting the potential value of incorporating foot structure analysis into individualized rehabilitation strategies.