Providing a New Parameter to Indicate the foot Alignment in People with Flat Feet

Flatfoot is characterized based on the height of medial longitudinal arch of foot relative to the ground. The most common methods employed to evaluate the severity of flatfoot and influences of foot insole on alignment of foot structure in static situation are foot print method and application of X-ray. However, both of them have some limitations and cannot be used during walking while subject uses insole. Therefore, the aim of this research was to find a parameter which represents the alignment of foot structure while walking. Two groups of normal and flat arch subjects were recruited in this study. The location of center of ankle joint (COJ) and center of pressure (COP) while walking was obtained by application of Qualysis motion analysis system and a force plate. The area between COP and COJ in the medial side to total area was the new parameter used in the present study. The mean value of the new parameter was 74.65±7.15 and 91.86±12.4 for normal and flatfoot subjects, respectively. It seems that the new parameter can be used to check the alignment of foot structure during walking. In flat arch subjects, the center of pressure located in the medial side. In contrast, in normal subjects the COP located mostly in the lateral side. Using foot insole translates the COP from medial side to lateral side.