Finite Element Simulation Of The Total Knee Joint In Different Motion States

The knee joint is the most biggest and complicated joint in the whole human body, lied between hip joint and ankle joint. And it is the junction for activities of human lower extremity. Anyone damage of the main components will result in abnormal movement of knee joint. As time passes, osteoarthritis of cartilage and meniscus will emerge because of wearing and degeneration, thereby normal activities of sufferers will be severely affected. Disease rate of all kinds of osteoarthritis,raises up unceasingly with age growing, including hip and knee joints'osteoarthritis. According to statistics, in crowd whose age above 50 year's old, 50 percent people suffered the osteoarthritis; in crowd whose age above 65 year's old, 90 percent female and 80 percent male suffered this disease. The osteoarthritis severely affects the old people's quality of life, even threatens their life; old patient not only suffer the pains, but bring many burden to family and society. At present, with economy development and improvement of living standard day by day, the low age people begin to suffer the osteoarthritis, and more and more people will be cursed by the osteoarthritis in the future.In view of the significance of knee joint and hazardless of related disease, researches on anatomical structure and corresponding biomechanical characteristics become more and more deep and extensive. Through the comparative study and analysis of normal and diseased knee joint, the disease occurred mechanism of knee joint can not only be better demonstrated, but can be guided to cure and rehabilitate related disease. But because of the complexity of anatomical structure in knee joint, the diversity of material properties composed of the knee joint, and the complexity of moving form and load distribution in every component in knee joint, therefore accurate description can't be made at present for biomechanical properties and behavior of knee joint.By near 40 year's development, finite element method already becomes the international main means in computational mechanics analysis for musculoskeletal system; but because of many articular surfaces, ligaments and muscles involved in knee joint, it is too difficult and too complex to built a complete finite element model for researching. Current research mainly concentrates on bones and important ligaments made up of knee joint, but studies on three-dimensional finite element model are fewer including complete bones and main ligaments of knee joint.In the light of these conditions, the main work in this paper is that : the motions of squat and gait are photographed,force distribution at the bottom of foot is obtained by experimental measurement, and the moments of the quadriceps are determined during the squat.; a three-dimensional finite element model above-mentioned is constructed to determine the stress distribution in articulation and ligaments of knee joint under different motions ( including squat, gait, and so on ) in this paper by finite element simulation method.Specific contents include the following several aspects:(1) A biomechanical model including simplified femur, tibia and menisci is built, and the contact pressure on articular cartilage of femur and tibia and contact pressure between femur and menisci are estimated preliminarily; and explicit analysis are done on mechanical properties of soft tissue, material properties, initial strain of ligaments and other data are given;the motions of squat and gait are photographed, the angle changed curves of some joints are obtained; at the same time, force distribution at the bottom of foot is obtained by experimental measurement, and the moments of the quadriceps are determined during the squat. (2) from the point of biomechanical view, based on CT scanning pictures of a volunteer's knee joint, a three-dimensional finite element model is constructed including complete femur, tibia, fibular, patellar, the cartilages and the main ligaments of knee joint. It is proved to be reasonable and valid by comparison with results of other theoretical models, experiments, and finite element models.(3) by using the above constructed finite element model, the stress distribution of articulation and ligaments of knee joint are calculated and analyzed under the conditions of double leg standing, squat and gait; and effects of loads coupled with motions on contact stress distribution are investigated. The results of the 0°～90°squat are that the peak value of contact pressure of cartilages and menisci would grow larger with the flexion angle increasing; the change of peak value of lateral meniscus is not significant relative to medial meniscus, and the peak values are smaller than that of medial.(4) The peak value of contact pressure of cartilages and menisci is the smallest in double legs standing, the largest value in the deep flexion 90°, and the peak value in single limb stance is larger than heel strike. And the tension force of ACL is larger than other ligaments in gait.Above all, a three-dimensional finite element model of the knee joint is constructed in this paper for the first time, including complete femur, tibia, fibular, patellar,main cartilage,menisci,and ligaments around the knee joint. The contact force for every articular surface and the stress distribution for ligaments of knee joint are researched by loading at the top femurios, based on morphological data of hip and ankle joints. It is proved to be reseanale and valid by comparing with research data of other scholars. Results of this paper give a operational platform for three-dimensional modeling of personal human knee joint and in vivo biomechanical studies; it also gives reference for insight to further to understand the mechanical behavior and function in every component of the knee joint under mechanical loads; it has significant meaning to understand the effects of daily activities on knee joint; and it has significant academic meaning and applicable value to develop replacement method of knee joint and to guide for clinical application.