Effect of body position on foot and ankle volume in healthy subjects

Physical therapy treatments for and evaluation of lower limb swelling are usually performed in supine lying position. However, the limb is usually treated or assessed in the dependent position, i.e. sitting or standing. The purpose of this study was to determine the possible confounding effect of subject positioning on foot and ankle volume. Sixty healthy individuals were randomly positioned into motionless standing, sitting or supine lying for 30 min. Volumetric measurements of the dominant leg were taken with a foot and ankle volumeter before and after 30 min of positioning. A significant difference between the three groups for foot and ankle volume change (F(2,53) = 35.41, P<0.001) was found. A post-hoc Tukey HSD test revealed that the difference was statistically significant between sitting and standing as well as supine lying and standing (P<0.001). No statistical significance was found between sitting and supine lying (P = 0.90). Standing caused the greatest increase in foot and ankle volume followed by sitting then supine lying. The results indicate that treating or assessing a limb with the subject in a sitting position would not be significantly different from a subject who is positioned in supine lying. However, it is not known whether the height and the distance from the heart to the feet were comparable between the groups, and so it is recommended that, where possible, treatment and assessment of lower leg swelling should be undertaken with the leg in a non-dependent position and definitely not in standing.