The kinetic and kinematic stability measures in healthy adult subjects with and without flat foot

Background Flat foot problems are associated with impaired mobility and postural stability. The purpose of this study was to compare the kinematic and kinetic indices during one leg standing between subjects with and without flat foot. Methods Forty-four participants enrolled in the study, including 22 subjects with flat foot and 22 control subjects. The measurements included kinematic stability on the trunk as well as kinetic stability from a force plate. All participants were asked to maintain one leg standing with the contralateral hip and knee flexed to approximately 90° for 25 seconds. Results The kinetic index decreased in the flat foot group (t = −5.08, p = 0.001) during one leg standing without visual input. There were strong correlations between kinetic and kinematic stabilities (0.75–0.86) with visual input and moderate correlations (0.49–0.67) without visual input in the control group. Discussion The flat foot group exhibited a significantly decreased kinetic index without visual input. The more effective postural stability in the control group might be due to efficient compensatory strategies utilized without visual input to maintain one leg standing. These outcome measures could help to develop a practical test leading to kinematic postural changes.