Forefoot pathology in relation to plantar pressure distribution in patients with rheumatoid arthritis: A cross-sectional study in the Amsterdam Foot cohort

Background: In patients with rheumatoid arthritis (RA), both high and low forefoot plantar pressures have been reported. Better understanding of pathology in the forefoot associated with altered pressure distribution in patients with RA could help to better formulate and specify goals for treatment with foot orthoses or therapeutic footwear. Objectives: To investigate the association of plantar pressure with disease activity and deformity in the forefoot in patients with rheumatoid arthritis and forefoot symptoms. Methods: A cross sectional study, using data of 172 patients with rheumatoid arthritis and forefoot symptoms, was conducted. Peak pressure (PP) and pressure time integral (PTI) in the forefoot were measured with a pressure platform. Forefoot deformity was assessed using the Platto score. Forefoot disease activity was defined as swelling and/or pain assessed by palpation of the metatarsophalangeal joints. The forefoot was divided in a medial, central and lateral region, in which the following conditions could be present: 1) no pathology, 2) disease activity, 3) deformity or 4) disease activity and deformity. A multilevel analysis was performed using condition per forefoot region as independent variable and PP or PTI in the corresponding region as dependent variable. Results: Statistically significant higher plantar pressures were found in forefoot regions with deformities (RR 1.2, CI 1.1-1.3, P