The relationship between foot and ankle symptoms and risk of developing knee osteoarthritis: data from the osteoarthritis initiative

Objective To investigate whether foot and/or ankle symptoms increase the risk of developing (1) knee symptoms and (2) symptomatic radiographic knee osteoarthritis (OA). Design 1020 Osteoarthritis Initiative (OAI) participants who were at-risk of knee OA, but were without knee symptoms or radiographic knee OA, were investigated. Participants indicated the presence and laterality of foot/ankle symptoms at baseline. The main outcome was development of knee symptoms (pain, aching or stiffness in and around the knee on most days of the month for at least 1 month in the past year). A secondary outcome was development of symptomatic radiographic knee OA (symptoms plus Kellgren and Lawrence [KL] grade ≥2), over the subsequent 4 years. Associations between foot/ankle symptoms and study outcomes were assessed by logistic regression models. Results Foot/ankle symptoms in either or both feet significantly increased the odds of developing knee symptoms (adjusted odds ratio (OR) 1.55, 95% confidence interval (CI) 1.10 to 2.19), and developing symptomatic radiographic knee OA (adjusted OR 3.28, 95% CI 1.69 to 6.37). Based on laterality, contralateral foot/ankle symptoms were associated with developing both knee symptoms (adjusted OR 1.68, 95% CI 1.05 to 2.68) and symptomatic radiographic knee OA (adjusted OR 3.08, 95% CI 1.06 to 8.98), whilst bilateral foot/ankle symptoms were associated with developing symptomatic radiographic knee OA (adjusted OR 4.02, 95% CI 1.76 to 9.17). Conclusion In individuals at-risk of knee OA, the presence of contralateral foot/ankle symptoms in particular increases risk of developing both knee symptoms and symptomatic radiographic knee OA.