Plantar pressures in people with midfoot osteoarthritis: cross-sectional findings from the Clinical Assessment Study of the Foot.

Midfoot osteoarthritis (OA) is a common condition, however its aetiology is not well understood. Understanding how plantar pressures differ between people with and without midfoot OA may provide insight into the aetiology and how best to manage this condition. To compare plantar pressures between people with and without symptomatic radiographic midfoot OA. This was a cross-sectional study of adults aged ≥ 50 years registered with four UK general practices who reported foot pain in the past year. Symptomatic radiographic midfoot OA was defined as midfoot pain in the last four weeks, combined with radiographic OA in one or more midfoot joints. Cases were matched 1:1 for sex and age (± 5 years) to controls. Peak plantar pressure and maximum force in 10 regions of the foot were determined using a pressure platform (RSscan International, Olen, Belgium) and compared between the groups using independent samples t -tests and effect sizes (Cohen's d). We included 61 midfoot OA cases (mean age 67.0, SD 8.1, 31 males, 30 females) and matched these to 61 controls (mean age 66.0, SD 7.9). Midfoot OA cases displayed greater force (d =0.79, medium effect size, p = <0.001) and pressure at the midfoot (d =0.70, me d ium effect size, p = <0.001), greater force at the fourth metatarsophalangeal (MTP) joint (d =0.28, small effect size, p = 0.13), and fifth MTP joint (d =0.37, small effect size, p = 0.10) and greater pressure at the fifth MTP joint (d =0.34, small effect size, p = 0.13). They also dis p layed lower force (d =0.40, small effect size, p = 0.02) and pressure at the hallux (d =0.50, medium effect size, p = <0.001) and lower force (d =0.54, medium effect size, p = <0.001) and pressure at the lesser toes (d =0.48, small effect size, p = <0.001) compare d with controls. Midfoot OA appears to be associated with lowering of the medial longitudinal arch, greater lateral push off and less propulsion at toe off. Longitudinal studies are needed to establish causal relationships. • People with midfoot OA displayed greater forces and pressures within the midfoot. • They had greater forces and pressures in the lateral forefoot and lower in the toes. • Midfoot OA appears associated with the lowering of the medial longitudinal arch. • It is also associated with greater lateral push off and less propulsion at toe off. • Future studies should assess interventions designed to normalise foot loading. [ABSTRACT FROM AUTHOR]