Ankle sprain is one of the most prevalent joint injuries in the lower extremity. Valid and reliable measurement techniques is essential for the collection of accurate and meaningful data about joint injuries such as ankle sprain. This case-control study is designed to evaluate the test-retest reliability of force plate measures and are compared the static postural control values in patients with chronic ankle instability (CAI), ankle sprain copers & healthy controls. Seventy-five patients (25 CAI, 25 copers & 25 healthy match controls) are asked to execute single-leg stance onto a force plate. Force plate parameters include, the center of pressure (COP) area, COP length, mean total velocity and sway index are measured for static postural control evaluation. To evaluate test-retest reliability, 20 participants of each group repeated the tests 6-8 days after the first session. Relative reliability of the force plate measures is assessed using interclass correlation coefficient (ICC) and absolute reliability using standard error of measurement (SEM), minimal metrically detectable change (MMDC) and coefficient of variance percent (CV%). Analysis of variance (ANOVA) is used to determine differences between three groups. Static postural control measures have high test-retest reliability, ranging from 0.73 to 0.88. Greater postural sway has been observed in the CAI compupd with the coper (P<0.05) and the matched limb of the control group (P(<)0.05). The results are illustrated that the static postural control measures are reliable tests to evaluate functional performance of the patients with CAI, copers and healthy controls.
