Objective:The purpose of this study was to study the distance of iliotibial band(iliotibial band,ITB)and lateral femoral condyle and the angle of ITB long axis with long femoral shaft in the condition of different knee flexion in normal young subjects. Method:One hundred asymptomatic volunteers (50 men and 50 women)participated in the study. The thickness and width of ITB were measured by sonographic and physical examination. The distance of ITB and lateral femoral condyle and the angle of ITB long axis with long femoral shaft were also measured in different the knee joint positions,which were extension,30°,90° and 135° flexion. Result:ANOVA shown that the average distance of ITB and the lateral femoral epicondyle varied significantly according to different positions of knee joint (P < 0.01)in either group. At the level of the lateral femoral condyle,ITB center gradually shifted from anterior to posterior of the lateral femoral condyle with the increasing of knee joint flexion. There was a significant difference in the average angle of ITB long axis with long femoral shaft according to different positions of knee joint using ANOVA(P < 0.01)in both groups. ITB axis gradually shifted from posterior to anterior of femoral shaft axis with the increasing of knee joint flexion. ITB average width and average thickness were statistically increased in male group using t-test(P < 0.01). ITB gradually shifts from anterior to posterior of femoral shaft with the incensement of knee joint flexion in healthy subjects. Conclusion:When knee joint occurs near 30° of flexion,the iliotibial band and the lateral femoral condyle friction is most prominent,which may one of causes of iliotibial band syndrome.