Trunk Lean Motion Strongly Affects the Lower Limb Position during Single-leg Standing

Abstract

[Objective] It is important to clarify the relationship between trunk posture change and lower limb position in predicting compensatory motion in patients with knee osteoarthritis. In this study, we investigated the effect of trunk lean motion on the position of the lower limbs during single-leg standing by measuring the mechanical axis inclination angle (MIA). [Methods] The participants included 11 healthy adult males. From the single-leg standing where the pelvis was held horizontally, the trunk was leaned in the ipsilateral and contralateral directions based on the supporting leg, and the changes in the MIA, center of mass (COM), and center of pressure (COP) were measured. [Results] The MIA during single-leg standing was strongly affected by trunk lean motion and decreased in the ipsilateral trunk lean and increased in the contralateral trunk lean. In addition, the COM was displaced in the direction of the trunk lean motion, but the position of the COP did not change. [Conclusion] The change in the MIA due to trunk lean motion considered to be the result of a postural strategy for maintaining the COP at a certain position, suggesting that the evaluation of the MIA is an important index for postural control.