Background and Aim: Standing stability is resulted by normal functioning of various neuro-muscular and musculo-skeletal systems. Patients with below knee amputation cannot use ankle strategy due to limb loss and they have to rely on other mechanisms to improve their standing stability. The effect of prosthesis foot on standing stability of patients with below knee amputation is not well understood. Therefore, the aim of this study was to evaluate the stability of below knee amputees and determine the influence of prosthesis foot on stability

Materials and Methods:  Fourty subjects participated in this study. Participants were divided into three groups including:  (a) normal individuals, (b) amputees using SACH foot and (c) amputees using single axis foot. The stability of subjects was evaluated by use of a Kistler force plate. The subjects were asked to stand on the force plate for one minute and look forward with their hand at their sides. The stability was evaluated by use of some parameters such as excursion of Center of Pressure (COP) and path length and velocity of COP in mediolateral and anteroposterior directions. The difference between the stability of the subjects was determined using One-way ANOVA and Post Hoc test.

Results: There was a significant difference between stability of the three groups during standing with regard to path length and velocity of COP in mediolateral and anteroposterior directions (P < 0.05). No significant difference was reported with regard to all of the measured parameters when comparing normal individuals and amputees with single axis foot (P >0.05).

Conclusion: Below-knee amputees standing stability who are using single axis foot have the same standing stability compared to normal subjects; moreover, stability of amputees who are using SACH foot was surprisingly better than normal subjects in some of the parameters including path length and velocity of COP in mediolateral and anteroposterior directions.

Keywords: Standing stability, Below knee amputation, SACH foot, Single axis foot, Force plate