While recent evidence suggests that foot pain may be related to mechanical stress, quantitative data elucidating the role of regional plantar loading in foot pain in individuals with midfoot osteoarthritis (OA) are lacking. Therefore the authors' objective is to examine regional plantar loading and self-reported foot pain in patients with midfoot OA compared to asymptomatic, matched control subjects.
Fifty subjects, 30 patients with midfoot OA and 20 control subjects participated in this study. Self-reported function was assessed using the Foot Function Index-Revised (FFI-R). Plantar loading during barefoot walking at self-selected, monitored walking speed was quantified using an EMED pedobarograph. Between-group differences in FFI-R score and plantar loading were assessed using an independent t-test and the Mann-Whitney U-test respectively. The relationship between FFI-R score and plantar loading was assessed using Spearman rank correlation. A k-means cluster analysis was used to identify potential sub-groups of patients through regional plantar loading.
The key findings of this study showed that patients with midfoot OA reported significantly higher FFI-R scores, and higher heel and medial midfoot average pressure compared to control subjects. Medial midfoot pressure-time integral was positively associated with FFI-R Pain Subscale Score (r=0.524, P<0.01). Based on the adequacy index, the two-cluster solution was deemed most appropriate.
This study demonstrated that patients with midfoot OA sustain increased magnitude and duration of regional plantar loading during walking compared to matched control subjects. Our findings support the theory that regional mechanical stress may be associated with symptoms in patients with midfoot OA. Future studies should assess whether interventions designed to reduce plantar loading are effective in relieving foot pain, and preventing progression of symptoms in patients with midfoot OA.