Background/Purpose:   Based on clinical observations, musculoskeletal foot disorders, such as hallux valgus or plantar fasciitis, appear to occur more frequently in a pronated foot type.  Other disorders, like hammer toes or Tailor’s bunions, may occur more often in a supinated (high arch) foot type.  The purpose of this cross-sectional analysis was to determine whether specific foot disorders were associated with over-pronated and over-supinated foot types in a large, bi-racial community-based cohort of men and women 50 years of age or older.

Methods:   Of 1,695 Johnston County Osteoarthritis Project participants clinically evaluated for foot disorders in 2006-2010, complete foot pressure data were available for 1,466 (1,425 with bilateral and 41 with unilateral foot data; mean age 68.5 years, mean body mass index [BMI] 31.2 kg/m², 67.2% women, 29.5% African American).  Two trained examiners used the validated Foot Assessment Clinical Tool to determine the presence or absence of foot disorders.  Foot pressure scans were recorded for both feet as participants walked at a normal pace over a Tekscan Matscan system (Tekscan Inc., Boston, MA).  The center of pressure excursion index (CPEI) was calculated for each foot.  CPEI cutoff values were set a priori to create a 3-category foot type variable: over-pronated (≤7.3), over-supinated (≥21.0), and neutral (>7.3 to <21.0; referent).  With the foot as the unit of analysis, separate multivariate logistic regression models using generalized estimating equations were performed to examine the association between foot type and each foot disorder, adjusting for age, BMI, gender, and race.  Effect modification between foot type and age, BMI, gender, or race were examined (p<0.10 for interaction was considered statistically significant).

Results: Of 2,891 feet available for analysis, 66.5% had a neutral foot type, 13.9% were over-pronated, and 19.7% were over-supinated.  Hallux valgus was the most common foot disorder (57.1%), followed by overlapping toes (27.1%), hammer toes (25.9%), Morton’s neuroma (6.0%), Tailors’ bunions (5.4%), plantar fasciitis (3.4%), and claw toes (2.1%).  Table shows results of adjusted models.  Compared to a neutral foot type, an over-pronated foot type was associated with hallux valgus (adjusted odds ratio [aOR]=1.36, 95% confidence interval [CI]=1.13-1.65) and overlapping toes (aOR=1.36, 95% CI=1.12-1.64), while an over-supinated foot type was inversely associated with hallux valgus (aOR=0.85, 95% CI=0.74-0.97).  These associations did not differ by age, BMI, gender, or race.

Conclusion:   Hallux valgus and overlapping toes were the only foot disorders strongly related to foot type in this sample.  Future studies should determine the longitudinal association between foot types and foot disorders as well as examine shoe and orthotic interventions for specific foot types as preventive approaches for foot disorders.

Table.

*Adjusted for age, BMI, gender, race.