Background: Although a lowered medial longitudinal arch has been cited as a causal factor in plantar fasciitis, there is little experimental evidence linking arch motion to the pathogenesis of the condition. This study investigated the sagittal movement of the arch in subjects with and without plantar fasciitis during gait.
Methods: Digital fluoroscopy was used to acquire dynamic lateral radiographs from 10 subjects with unilateral plantar fasciitis and 10 matched control subjects. The arch angle and the first metatarsophalangeal joint angle were digitized and their respective maxima recorded. Sagittal movement of the arch was defined as the angular change between heel strike and the maximum arch angle observed during the stance phase of gait. The thickness of the proximal plantar fascia was determined from sagittal sonograms of both feet. ANOVA models were used to identify differences between limbs with respect to each dependent variable. Relationships between arch movement and fascial thickness were investigated using correlations.
Results: There was no significant difference in either the movement or maximum arch angle between limbs. However, subjects with plantar fasciitis were found to have a larger metatarsophalangeal joint angle than controls (P < 0.05). Whereas the symptomatic and asymptomatic plantar fascia were thicker than those of control feet (P < 0.05), significant correlations were noted between fascial thickness and peak arch and metatarsophalangeal joint angles (P < 0.05) in the symptomatic limb only.
Conclusions: Neither abnormal shape nor movement of the arch are associated with chronic plantar fasciitis. However, arch mechanics may influence the severity of plantar fasciitis, once the condition is present. Digital flexion, in contrast, has a protective role in what might be a bilateral disease process.