Effect of Fatigue on Knee Kinematics and Kinetics During Walking in Individuals With Flat Feet

Flat feet areassociated with altered knee kinematics, kinetics, and knee pain.Fatigue of plantar intrinsic foot muscles mayincrease the navicular drop. However, it is not clear how fatigue may influence the knee pain in individuals with flat feet.The purpose of this study was to assess the effect of fatigue on knee kinematics and kinetics in flatfeet during walking. This is a quasi-experimental research. Ten flat feet individuals(age: 24.4±2.16Yrs;height: 177.2±4.31cm;mass: 81.9±17.4Kg), and 10 normal subjects (age: 25.28±6.33Yrs;height: 168.61±27.71cm;mass: 78.13±26.93Kg) were participated in this study, randomly. A Vicon motion analysis system (100 Hz) with four cameras and as well as two Kistler force plates (1000 Hz) were used to measure knee kinematics and kinetics during gait which were repeated after fatigue. For between group and within group comparisons independent t-test and Repeated Measure analysis of variance were used, respectively. SPSS software (version 22) was used to analyze datat with the significance level of p Knee range of motion of Flatfeet group in frontal plane (9.37º±2.54º)was significantly higher than that of Healthy group (p=0.01) in pretest. In Flatfeet group, the knee moment in sagittal, frontal and horizontal plan was significantly greater than those in Healthy group by 0.86 (p= 0.002), 0.25 (p= 0.016) and 0.19 (p= 0.000) Nm/BW, respectively in pretest. Adductor moment increased after fatigue protocol in Healthy group by 0.08 Nm/BW. Before exhaustion, the knee moments in sagittal, frontal, and horizontal planes in the Flatfeet group were significantly higher than that of Healthy group. In Flatfeet group, fatigue resulted in a decrease on the knee flexion and abduction moments and increase on knee ROM in sagittal and frontal plane in flat foot group. The decreased knee muscle moments may result in an increased loading on the knee joint. It appears that extreme exhausting activity might place the knee of Flatfeet individuals at the risk of pathology and injury.