Standing Stability Evaluation in Subjects with Flat Foot

Flat foot is one of the most common disorders which not only influences the performance of the foot, but also affects the alignments of the ankle, knee and hip joints. The performance of flat arched differs from that of normal subjects during walking. However, there is not enough information in the literature regarding the difference between standing stability. Moreover, the influence of use of foot insole on standing stability has not been yet evaluated. This study was aimed to investigate the stability of subjects with flat foot with and without insole.

Forty female students in Isfahan University of Medical sciences participated in this study. Then they classified into two equal groups of twenty normal and flat arched individual. Center of pressure (COP) was measured using Kistler force plate. The stability was evaluated by calculating the COP excursions, path length, and velocity in the mediolateral and antroposterior directions. The differences between stability of normal and flat foot subjects with and without insole were evaluated by use of sample and paired t-test, respectively (α = 0.05).

There was a significant difference between the stability of flat arched and normal subjects based on COP velocity and total velocity (P < 0.05). However, there was not a direct correlation between the severity of flat foot and instability during quiet standing (P > 0.05). The mean values ± SD of COP total velocity during standing with and without insole were 1645.42 ± 160 and 2752±683 mm/min, respectively (P < 0.001).

The flat foot is more unstable compared with normal subjects during quiet standing due to miss-alignment of foot structure and a decrease in proprioception awareness of the foot ligaments and tendon. Insole can help to align foot structure and also reduce the exceed forces applied on the ligament and finally improves the standing stability.