Effect of Leg Length Inequality on Upright Posture

Abstract

The purpose of this investigation was to examine how leg length inequality induces morphological changes in pelvis and lumbar vertebra, and load difference between right and left legs in an upright posture. Twenty healthy subjects (11 men and 9 women) stood with the both legs 30 cm apart putting on different weight-meters, and leg length inequality of 3, 6, 9, 15, 21, 30 and 55 mm was artificially made. Load difference between right and left legs was measured, and the angle of torsion was also measured in pelvis and spine of 4 subjects. In the case of leg length inequality of 10 - 20 mm, subjects were found to maintain the vertical equilibrium by alternating torsion (rotation) and lateroversion of pelvis and spine, and tended to transfer a center of gravity to the side of a long leg. In the case of leg length inequality of over 30 mm, they could not keep an upright posture due to a loss of equilibrium sense. These indicate that those who with a leg length inequality try to keep an upright posture by alternating torsion and lateroversion of pelvis and spine, thereby possibly inducing poor postures. It was also suggested that a right leg may play a more dominant role in keeping the equilibrium, compared with a left leg.