Reliability of navicular displacement measurement as a clinical indicator of foot posture.

This study evaluated two methods for quantifying foot posture: navicular drop and navicular drift. Five clinicians measured 20 nonpathological participants on two occasions. Intraclass correlation coefficients ranged from 0.33 to 0.76 for navicular drop and from 0.31 to 0.62 for navicular drift. The standard error of measurement, as a 95% confidence interval, ranged from +/-1.5 mm to +/-3.5 mm for navicular drop and +/-3 mm to +/-5 mm for navicular drift. Intratester reliability was slightly better than intertester reliability for both measurements. These results indicate that both techniques are only moderately reliable, and physicians using these measurements in clinical practice should interpret the values in light of the magnitude of error associated with them.