Background/Purpose . Foot pain is associated with poorer physical function in older adults, but few studies have examined how foot structure (high / low arches) and foot function (supination / pronation) are related to lower extremity physical function. The purpose of this cross-sectional study was to evaluate whether foot structure and function were associated with self- reported and performance-based physical function in a community-based study of Caucasian and African American men and women 50+ years old.

Methods . During the 2006-2010 exam of the Johnston County Osteoarthritis Project, foot pressure scans were obtained and  physical function of participants was assessed via self-report and performance tests.  Physical function measures included: the Foot and Ankle Outcome Score –Activities of Daily Living subscale (FAOS-ADL, 0 – 100 [extreme – no limitation]), 5 timed chair stands (unable and quartiles of completion time in seconds [s]), 8-foot walk (unable and quartiles of time in s), and standing balance (unable to stand without assistance, <10 s semi-tandem, semi-tandem 10 s but unable full tandem >2 s, full tandem 3-9 s, and full tandem 10 s). Foot pressure scans were used to determine foot structure (modified arch index) during standing and foot function (center of pressure excursion index) while walking. Based on population data, foot structure was categorized as high arch, low arch, and referent; foot function was categorized as over-pronated, over-supinated, and referent. The most extreme foot structure and function for each participant were used in analyses. Separate linear (continuous outcomes) and logistic (categorical outcomes) regression models were used to estimate the associations between foot types and physical function measures, adjusting for age, body mass index [BMI], sex, and race.

Results . 1571 participants had foot structure data and 1490 had foot function data (mean age 69 years, mean BMI 32 kg/m², 68% women, 30% African American). In standing, 22% had a low arch and 39% had high arch; during walking, 22% had an over-pronated foot and 31% had an over-supinated foot. Compared to the referent foot structure, higher FAOS-ADL scores (better physical function) were associated with a high arch in adjusted models, while a low arch was associated with worse physical performance on the chair stand and 8-foot walk tasks and with poorer balance (Table); these results were attenuated after controlling for age, BMI, sex, and race. Compared to the referent foot function, an over-supinated foot was associated with a faster 8-foot walk speed.  

Conclusion . A high arch and an over-supinated foot were related to better lower extremity physical function.  Longitudinal studies are needed to examine the effect of foot structure and function on changes in physical function and to assess interventions for modifying foot type (e.g., shoe orthotics) to limit physical decline in populations.