BACKGROUND:
Plantar fasciitis is one of the more common soft-tissue disorders of the foot, yet little is known about its etiology. The purpose of the present study was to use an epidemiological design to determine whether risk factors for plantar fasciitis could be identified. Specifically, we examined the risk factors of limited ankle dorsiflexion with the knee extended, obesity, and time spent weight-bearing.

METHODS:
We used a matched case-control design, with two controls for each patient. The matching criteria were age and gender. We identified fifty consecutive patients with unilateral plantar fasciitis who met the inclusion criteria. The data that were collected included height, weight, whether the subject spent the majority of the workday weight-bearing, and whether the subject was a jogger or runner. We used a reliable goniometric method to measure passive ankle dorsiflexion bilaterally. The main outcome measure was the adjusted odds ratio of plantar fasciitis associated with varying degrees of limitation of ankle dorsiflexion, different levels of body mass, and the subjects' reports on weight-bearing.

RESULTS:
Individuals with < /=0 degrees of dorsiflexion had an odds ratio of 23.3 (95% confidence interval, 4.3 to 124.4) when compared with the referent group of individuals who had >10 degrees of ankle dorsiflexion. Individuals who had a body-mass index of >30 kg/m (2) had an odds ratio of 5.6 (95% confidence interval, 1.9 to 16.6) when compared with the referent group of individuals who had a body-mass index of < /=25 kg/m (2). Individuals who reported that they spent the majority of their workday on their feet had an odds ratio of 3.6 (95% confidence interval, 1.3 to 10.1) when compared with the referent group of those who did not.

CONCLUSIONS:
The risk of plantar fasciitis increases as the range of ankle dorsiflexion decreases. Individuals who spend the majority of their workday on their feet and those whose body-mass index is >30 kg/m (2) are also at increased risk for the development of plantar fasciitis. Reduced ankle dorsiflexion, obesity, and work-related weight-bearing appear to be independent risk factors for plantar fasciitis. Reduced ankle dorsiflexion appears to be the most important risk factor.



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