Measuring Structural and Functional Characteristics of the Medial Longitudinal Arch: Building a Classification System

Abstract

Historically, foot type has been classified on a single, linear continuum ranging from flat, to normal, to high, with minimal distinction made between differences in the medial longitudinal arch (MLA) orientation in different postures or tasks. Structural arch data has been recorded in various static positions, but functional assessment typically relies on methodologies that are difficult to replicate en mass. Because of this, a classification scheme that independently evaluates structural and functional foot arch characteristics using a simple field tool is required. A mirror box unit was used to record images of participant’s footprints while they were in a sitting, standing, and partial squat position in order to progressively deform the MLA. Differences in Arch Index scores from the weighted (standing and partial squat) and unweighted (sitting) position were used to determine MLA function. Observable changes between positions were detected, indicating that functional arch type can be measured using quasi-static techniques. Accounting for both structural and functional arch characteristics will allow practitioners to be more targeted when training or treating individuals in the future. The methodology used in this study also showed that MLA deformation is impacted by body position, thus requiring standardized protocols for future data collection if results are to be considered comparable going forward.