MECHANICAL STRESS IN KNEE JOINT DURING RUNNING AT VARIOUS SPEEDS AND STEP LENGTHS

Abstract

In order to give more effective instruction for running in sports medicine, the mechanical stresses in the knee joint during running at various speeds and step lengths were investigated.
The subjects were five male sprinters. Running conditions were as follows : 1) running at four speeds (2.5 m/s, 4.5 m/s, 6.5 m/s and maximum running speed) with natural step lengths, 2) run-ning with three different step lengths (1.0 m, 1.5m and preferred step length) at 4.5 m/s running speed, and 3) running at maximum speed using four different step lengths (1.0 m, 1.5m 2.5m and preferred step length) . Running movements were recorded using a high speed video camera. And ground reaction forces were also measured by a force platform. The compressive force and shear force in the tibiofemoral joint were computed from the results of two dimensional motion analysis. That is, the external force caused by ground reaction forces, the internal force produced by the mus-cle to develop joint torque and total force (external+internal force) were computed for both com-pressive and shear forces.
The total compressive force that affects the meniscus and articular cartilage in the tibiofemoral joint depended on the magnitude of internal force. The total compressive force increased with running speed and step length. Therefore, caution should be employed in changing running speed and step length for regulating the magnitude of total compressive force on the tibiofemoral joint. On the other hand, the total shear force that caused traction stress in the posterior cruciate ligament depended on the magnitude of external force. The posterior shear force was generated during the foot contact period, and increased with step length. As for total shear force in the tibiofemoral joint, care must be taken to regulate step length.