Impact of Concurrent Foot Pain on Health and Functional Status in People with Knee Osteoarthritis: Data from the Osteoarthritis Initiative

Objective: To document the prevalence of foot pain and foot pain laterality in people with knee osteoarthritis (OA) and to examine its impact on health and function.

Methods: Participants from the Progression subcohort (n = 1,255, ages 45-79 years) of the Osteoarthritis Initiative with symptomatic tibiofemoral knee OA were included. Prevalence of foot pain, defined as pain in the foot/ankle, and foot pain laterality were determined. Health status was evaluated using the Western Ontario and McMaster Universities Osteoarthritis Index, the Short Form-12 Health Survey, and the Center for Epidemiological Studies Depression Scale. Function was assessed using the 20-meter walk test (WT) and a repeated chair stand test. Differences in health and functional measures were compared between groups with and without foot pain using multivariate analysis of covariance.

Results: One-fourth (n = 317 [25%]) of people with knee OA experienced concurrent foot pain, with the majority (n = 174 [55%]) reporting pain in both feet. After adjusting for covariates, people with foot pain scored worse on all health measures and on the 20-meter WT, compared to those without (P < 0.05). Differences in health and function were found between the bilateral and ipsilateral foot pain groups compared to those without foot pain (P < 0.05), but no differences were found with the contralateral group.

Conclusion: Foot pain is common in people with knee OA, and bilateral and ipsilateral foot pain adversely affect health and function, suggesting laterality is important. Further research is needed to establish the mechanism and interaction of pathology at these sites and to evaluate foot pain treatment in this population.