Foot posture is associated with plantar pressure during gait: A comparison of normal, planus and cavus feet

Background: Variations in foot posture, such as pes planus (low medial longitudinal arch) or pes cavus (high medial longitudinal arch) are associated with some lower limb injuries. However, the mechanism that links foot posture to injury is not clear. Research question The aim of this study was to compare plantar pressure between healthy individuals with normal, planus or cavus feet. Methods: Ninety-two healthy volunteers (aged 18 to 45) were classified as either normal (n = 35), pes planus (n = 31) or pes cavus (n = 26) based on the Foot Posture Index, Arch Index and normalised navicular height truncated. Barefoot walking trials were conducted using an emed (R) - x400 plantar pressure system (Novel GmbH, Munich, Germany). An 11 region mask was used that included the medial heel, lateral heel, midfoot, 1st, 2nd, 3rd, 4th and 5th metatarsophalangeal joints, hallux, 2nd toe, and the 3rd, 4th and 5th toes. Peak pressure, pressure-time integral, maximum force, force-time integral and contact area were calculated for each region. One way analyses of variance and effect sizes were used to compare the three foot posture groups. Results: Overall, the largest differences were between the planus and cavus foot groups in forefoot pressure and force. In particular, peak pressures at the 4th and 5th MTPJs in the planus foot group were lower compared to the normal and cavus foot groups, and displayed the largest effect sizes. Significance This study confirms that foot posture does influence plantar pressures, and that each foot posture classification displays unique plantar pressure characteristics.