Joint stabilising response to lateral and medial tilts

Background Joint stabilisation processes have been mainly studied comparing groups or joints with different stabilities and mainly focusing on one single parameter. The inherent limitations are discussed and a study, where kinematic, kinetic and electromyografic parameters gained from sudden tilt tests were measured, is presented. Methods The response of 24 subjects to sudden lateral and medial tilts of the foot during one legged stance were compared. A three-dimensional foot model was utilised to describe ankle and foot motion. Electromyografic signals of six muscles of the lower limb as well as the horizontal ground reaction forces were analysed. Findings Forefoot to rearfoot motion was faster and greater than ankle motion. In general medial tilts showed lower motion amplitudes and angular velocities than lateral tilts but higher horizontal ground reaction force integrals. The electromyography patterns where similar for both conditions. However, a specificity of the muscular response could be identified in the electromyography amplitudes. Interpretation The higher mediolateral ground reaction forces, together with the reduced kinematic and no general increase in muscular activation in medial tilts suggest, that passive structures seem to be able to counteract destabilising forces and thus reduce the otherwise needed muscular activation.