Relationship between obesity and foot pain and its association with fat mass, fat distribution, and muscle mass.

Objective: To examine the relationship between obesity, body composition, and foot pain as assessed by the Manchester Foot Pain and Disability Index (MFPDI).

Methods: Subjects 25-62 years of age (n = 136) were recruited as part of a study examining the relationship between obesity and musculoskeletal health. Foot pain was defined as current foot pain and pain in the last month, and an MFPDI score of ≥1. Body composition (tissue mass and fat distribution) was measured using dual x-ray absorptiometry.

Results: The body mass index (BMI) in this population was normally distributed around a mean of 32.1 kg/m(2). The prevalence of foot pain was 55.1%. There was a positive association between BMI and foot pain (odds ratio [OR] 1.11, 95% confidence interval [95% CI] 1.06-1.17). Foot pain was also positively associated with fat mass (OR 1.05, 95% CI 1.02-1.09) and fat mass index (FMI; OR 1.16, 95% CI 1.06-1.28) when adjusted for age, sex, and skeletal muscle mass and age, sex, and fat-free mass index (FFMI), respectively. When examining fat distribution, positive associations were observed for android/total body fat ratio (OR 1.42, 95% CI 1.11-1.83) and android/gynoid fat ratio (OR 35.15, 95% CI 2.60-475.47), although gynoid/total body fat ratio was inversely related to foot pain (OR 0.83, 95% CI 0.73-0.93). Skeletal muscle mass and FFMI were not associated with foot pain when adjusted for fat mass or FMI, respectively.

Conclusions: Increasing BMI, specifically android fat mass, is strongly associated with foot pain and disability. This may imply both biomechanical and metabolic mechanisms.