Abstract
The purpose of this study was to examine the effect of fixed / unfixed knee joint on single-leg standing balance, and to identify those who are considered to have a high risk of ankle re-injuries among people with chronic ankle instability (CAI). We compared the center of pressure (COP) and head and foot accelerations of healthy and CAI groups under the fixed and non-fixed conditions of the knee joint in the single leg standing posture with eyes closed. Based on the changes of the medio-lateral acceleration of head between two conditions, the CAI group was divided into two sub-groups, and the balance ability was evaluated. It became more difficult to maintain the posture with the knee-joint-fixed condition, but expressions were different between two groups. Among the CAI group, those with high head acceleration change seemed to have ankle instability that was masked by movement of hip joint via kinematic chain. Those who showed high change in head acceleration in constrained single-leg standing may have a higher risk of ankle sprain re-injury.
