Articular ankle joint loading during dynamic activities

Abstract

Increased joint contact stress can lead to cartilage degeneration and thus the development of osteoarthritis. While articular knee joint loading is well studied [1], less is known about other joints despite them being at risk of the disease as well. In particular, structural deformities of the foot-ankle complex such as flat feet are known to increase the risk for developing osteoarthritis at the hind- and midfoot joints [2]. The aim of this project was to combine state of the art in vivo kinematics with dynamic musculoskeletal simulations using an extended foot-ankle model including contact modelling to estimate ankle articular joint loading in healthy subjects during different gait activities. 6 healthy subjects (4 female, 2 male; 23.8±3.0 years; BMI 23.2±2.4 kg/m²) with no history of foot-ankle injuries participated in this study. Whole body kinematics were measured for each subject during three gait cycles of walking and running using a full body and extended foot skin marker system [3]. Cartilage contact between the tibia and talus were added to a foot-ankle model [4] to allow estimation of articular joint mechanics using an elastic foundation model based on cartilage stiffness and mesh penetration [1]. Generic models were scaled for each individual and kinematics calculated for every trial. Based on subject-specific kinematics, articular joint mechanics were estimated using the OpenSim joint and articular mechanics (JAM) tool [1]. To investigate articular joint loading, contact area as well as mean and peak pressure at the ankle joint were analysed during the stance phase. Mean and peak cartilage contact pressure were comparable at heel strike and toe off, but substantially differed throughout the stance phases of walking and running (Fig. 1A). During walking, cartilage contact pressure showed a double peak with the higher peak around contralateral heel strike (peak pressure: 5.96±1.66 MPa) whereas during running cartilage contact pressure showed a single peak during mid-stance (peak pressure: 9.61±2.41 MPa) (Fig. 1A&B). Although similar cartilage contact locations were found for walking and running, contact area was considerably larger during running (1.39±0.15 cm²) then walking (0.96±0.19 cm²) (Fig. 1B).Download : Download high-res image (119KB)Download : Download full-size image This study showed a first analysis of ankle mechanics during multiple gait cycles of walking and running. Using a detailed musculoskeletal foot-ankle model combined with recently developed methods to estimate cartilage contact mechanics, this study allowed novel insights on the location and magnitude of articular joint loading. While this study provided important findings on the ankle joint, further developments are needed to also estimate cartilage contact mechanics at the subtalar joint. In addition, analysis of pathological cohorts such as subjects with chronic ankle instability or flat feet, will help to understand changes in articular mechanics and how they are related to cartilage degeneration.