膝関節のバイオメカニクスと動筋・拮抗筋力

抄録

The anterior-posterior displacement of the tibia elicited by the loading of the quadriceps and hamstring muscles was determined as a function of joint angle and muscle load using the data collected from five fresh cadaver knees with a highly accurate computerized radio-graphic technique. A two-dimensional mathematical model, taking into account movements and forces of the patellofemoral and tibiofemoral joints in the sagittal plane, was described and a computer simulation was performed to verify the experimental results. The simulated and experimental results closely coincided. Both the results demonstrated that quadriceps contraction can result in an anterior displacement of the tibia in the range of 0°to 40°of flexion, and in a posterior displacement in the range of 80°to 120°of flexion. However, hamstrings contraction always causes a posterior displacement of the tibia, irrespective of knee flexion angle. Thus it was concluded that quadriceps contraction has a direct impact on ACL stress, as hamstring contraction does on PCL stress. It was further concluded, however, that the absolute magnitudes of both the cruciate ligaments were not so much influenced by the thigh muscles' contraction as they were influenced by knee flexion angle, a conclusion that throws into question the assessment of cruciate ligament stresses by anterior-posterior displacement of the tibia. Some useful parameters that serve as a function of knee flexion angle were also introduced through the simulation: contact force and slipping ratio of the patellofemoral and tibiofemoral joints, variation of the patellar ligament force, and thigh muscle length. There is a linear relationship between quadriceps muscle force and patellofemoral contact force, whereas there is little relationship between quadriceps muscle force and tibiofemoral contact force. A semilinear relationship is observed between knee flexion angle and patello-femoral contact force. The tibiofemoral contact force shows a bell-shaped pattern against knee flexion angle. Variation of the patellofemoral slipping ratio shows a complex form in which the glide and roll of the patella on the femur take place in the opposite direction for 0°to 95°of knee flexion while glide and roll take place in the same direction for more than 95°of flexion. Variation of tibiofemoral slipping ratio shows that the femur mainly glides on the same position of the tibia between 30°and 90°of knee flexion. Linear relationships do exist between knee flexion angle and, respectively, quadriceps length and hamstrings length. Patellar ligament force varies from a similar value to about 60% of the quadriceps force as the knee flexes.