STUDY DESIGN: Controlled laboratory study. OBJECTIVE: To explore potential associations between foot posture index (FPI-6) composite scores and dynamic plantar pressure measurements, and to describe each of the 6 subscales and the FPI-6 composite scores across our sample. BACKGROUND: The FPI-6 is a static foot posture assessment comprised of 6 observations. Extreme scores have been associated with increased injury risk. However, knowledge describing the relationship between FPI-6 scores and plantar pressure distributions during gait is limited. METHODS: Participants (n = 1000; 566 males, 434 females) were predominantly active adults (mean ± SD age, 30.6 ± 8.0 years; body mass index, 26.2 ± 3.7 kg/m²), who ran 3.1 ± 1.4 d/wk. Static and dynamic foot characteristics were compared using the FPI-6 and a capacitance-based pressure platform. Correlation and hierarchical stepwise regression analyses were performed to determine the most parsimonious set of dynamic pressure data associated with FPI-6 scores. RESULTS: The mean ± SD FPI-6 score was 3.4 ± 2.9 (range, –6.0 to 11.0). Only 31 participants received a score of –2 (supinated foot) on any FPI-6 subscale. Classification of a pronated foot was 2.4 times more likely than a supinated foot. A 5-variable model (R = 0.57, R² = 0.32) was developed to describe the association between dynamic plantar pressures and FPI-6 scores. CONCLUSION: The multivariate model associated with FPI-6 scores comprised clinically plausible variables which inform the association between static and dynamic foot postures. Different cutoff values may be required when using the FPI-6 to screen for individuals with supinated feet, given the limited number of high-arched participants identified by FPI-6 classifications.

J Orthop Sports Phys Ther 2011;41(2):100-107, Epub 22 October 2010. doi:10.2519/jospt.2011.3412

KEY WORDS: anthropometrics, arch height, foot, foot posture index, podography