Normal values of the Foot Posture Index in a young adult Spanish population: a cross-sectional study.

BACKGROUND: Although the appearance of foot or lower-limb pathologies is etiologically multifactorial, foot postures in pronation or supination have been related to certain diseases such as patellofemoral syndrome and plantar fasciitis. The objective of the present study was to determine the normal values of foot posture in a healthy young adult Spanish sample, and to identify individuals at risk of developing some foot pathology.
METHODS: The Foot Posture Index (FPI) was determined in a sample of 635 (304 men, 331 women) healthy young adults (ages 18-30 years). The FPI raw score was transformed into a logit score, and a new classification was obtained with the mean ± 2 SD to identify the 5% of the sample with potentially pathologic feet.
RESULTS: The normal range of the FPI was -1 to +6, and FPI values from +10 to +12 and -6 to -12 could be classified as indicating potentially pathologic feet. The women's logit FPI (0.50 ± 1.4, raw FPI +3) was higher than the men's (0.25 ± 1.6, raw FPI +2), with the difference being significant (P = 0.038). No statistically significant differences were found between body mass index groups (P = 0.141).
CONCLUSIONS: The normal FPI range goes from just one point of supination to a certain degree of pronation (+6). The identification of 35 individuals with potentially pathologic feet may help in the implementation of a preventive plan to avoid the appearance of foot disorders.