Abstract
The purpose of this study was on the one hand, basic research into the knee in and toe out leg position lessening stress on the anterior cruciate ligament (ACL), and also the clarification of a factor resolving the contradiction of so-called easily occurring, non-contact type ACL injuries in this position. With 20 healthy females (average age, 21.6 ± 4.6) as subjects we measured the ground reaction force in one step movement with 3 dynamic alignments: knee in & toe out, knee out & toe in, and a neutral position with the knee and foot facing forward. In one step movement, the ground reaction force of knee out & toe in acted more in the lateral direction than that of the neutral position. In contrast, knee in & toe out ground reaction force acted inwardly to the rear, and additionally, at the time of movement, front-rear braking effort was poor. According to the results, we consider that in knee out & toe in, because a lateral shear force was generated on the femur which was receiving lateral torque from the tibia, tension on the ACL was heightened by toe in, making ACL injury easier to occur. Also, in knee in & toe out we consider that as stresses build up simultaneously, and shear force is generated in the forward direction on the femur, which is receiving torque in the forward direction from the tibia, which is exhibiting weakened brake force in the forward direction, ACL injury incidence would be higher.
