Therapeutic, Level II: Prospective, comparative trial.

Flat foot is the most common foot disorder that influences the alignment of the lower limb structure. It is controversial whether the use of foot insole influences kinetic and kinematic of the leg or not. Therefore, this study investigated the influence of foot insole on the gait performance in subjects with flat foot disorder. A group of flat foot subject was recruited into this study (the number of subjects was 15). The motion of the leg joints was determined using the Qualysis motion analysis system. Moreover, the force applied on the lower limb was recorded by a Kistler force plate. The range of motion of the lower limb joints, the moments applied on the lower limb joints and force transmitted through the leg were the parameters used in this study. The difference between these parameters during walking with and without insole was evaluated using the paired [Formula: see text]-test. Significant value was set at [Formula: see text]. There was no significant difference between the range of motion of ankle joint while walking with and without insole. However, the medial directed force applied on the leg decreased significantly [Formula: see text]. The use of foot insole did not influence the moments transmitted through the hip and knee joints. The walking speed of the subjects improved while walking with foot insole. Use of foot insole influenced the magnitude of the force applied on the leg and the adductor moment of ankle joint due to its influence on foot alignment. As the walking speed of the improved subjects follows the use of insole, it can be concluded that it may have a positive effects on the performance of flat foot subjects.

Background and aim: Flatfoot is characterized based on the height of the medial longitudinal arch of the foot relative to ground. The most common methods used to evaluate the severity of flatfoot and influences of the foot insole on the alignment of the foot structure in static situation are footprints and the use of X-ray. However, both of them have some limitations and cannot be used during walking while the subject uses the insole. Therefore, the aim of this research was to find a parameter which represents the alignment of the foot structure while walking. Methods: Two groups of normal and flat-arched subjects were recruited into this study. The location of center of ankle joint (COJ) and center of pressure (COP) while walking was obtained using Qualysis motion analysis system and a force plate. The area between COP and COJ in the medial side to the total area was the new parameter used in this study. Conclusion: The mean value of the new parameter was 74.65 ± 7.15 and 91.86 ± 12.4 for normal and flatfooted subjects, respectively. It appears that the new parameter can be used to check the alignment of the foot structure during walking. Clinical statement: The results of this research study can be used by clinicians to determine the alignment of the foot structure and the influence of the foot insole.