Is a Footwear Fit Volumetric Index Significantly Associated with Foot Pain?

Background: Foot pain is associated with multiple risk factors like footwear. One factor that can lead to inadequate footwear being chosen is failure to consider the changes in volume that occur in the foot. So, could the establishment of a Footwear Fit Volumetric Index (FFVI)) contribute to our understanding of the significant association between footwear fit and foot pain? Objective. To establish an FFVI and to determine whether this index is significantly associated with foot pain. Methods: A cross-sectional study was carried out from March 2021 to January 2022. In total, 457 participants were recruited and completed the Foot Function Index and Visual Analog Scale (foot pain) questionnaires. Anthropometric measurements were obtained using a foot measurement platform, and foot posture was assessed using the Foot Posture Index. Results: Overall, 40.7% of participants were male, and 59.3% were female. The participants had a mean age of 39.06 years and a body mass index of 25.58 Kg/cm². Their shoe sizes ranged from 37 to 47 (median 40 (IQR: 5). The median FFVI values for the right foot (load-bearing vs. non-load-bearing) were 884.58 (IQR: 328.07) and 898.77 (IQR: 337.45), respectively. The correlation between the FFVI and shoe size was strong and statistically significant in the right foot, load-bearing (rho = 0.842; p < 0.001) and non-load-bearing (rho = 0.878; p < 0.001). A significant inverse relation was detected between the FFVI and foot pain in both feet (p < 0.001). Conclusions: The FFVI is significantly associated with foot pain. As the FFVI increases (suggesting a better footwear fit), foot pain decreases. Our findings have important clinical applicability, as they highlight the importance of optimizing footwear fit as a strategy to prevent and treat foot pain.