Dynamic Simulation Of Knee Joint's Mechanical Properties

Biomechanics is mechanics applied to biology. Biomechanics is a marginal and crossed discipline, which is formed as a result of combination and convergence of mechanics, biology, physiology and other discipline. Biomechanics seeks to understand the mechanics of living systems. From the view of life individual, tissue, organ, cell and the different hiberarchy of molecule, it studies the relations between stress and motion, distortion, flow, and growth.Arthritis is a common orthopaedic disease, especially for the knee. Now the most effective surgical treatment is to do the joint replacement surgery ,but there were so many divarication on the operation of the knee due to the poor knowledge about the mechanical properties of knee, such as the surgical scheme of ligament injuries, the choose and insert position of the prosthesis and how to deal with the patella. In recent 20 years, the overhaul ratio of artificial knuckle was up to 15-20%, so it was very important to descent it and to optimize the prosthesis.It was very difficult to measure the ligaments force directly because the knee joint is encapsulated, so there were so many mathematic model used to get the force. However, these models were simplified without the relationship of the ligaments, muscle and the bone, and most of them were 2D models, and some 3D models were not based on the real joint geometry and the results were different with each other. And there was no a uniform dynamic conclusion for the normal knee joints in walking and bending.The purpose of this study was to simulate the knee joint motion during walking and bending dynamically, and analyze the pattern of contact force and ligament force in ACL-deficient and PCL-deficient knee in the different motion. The study could improve the knowledge about the dynamic property of the knee joint and would be helpful to surgery. In this paper, based on the kinematic and dynamic simulation software LifeMod (BRG Corp), the lower limb model of human including ligaments and muscles was established and used to simulate the human motion in normal gait and bending dynamically, and the effects of ACL-deficiency and PCL-deficiency are also considered.After the dynamic simulation, the contact force between the tibiofemoral joint and ligaments tensile force both in normal gait and bending are gotten. During the bending, the maximum contact force is 2747N, about 3.10BW (Body Weight), and the maximum ligament tensile force is 492N, which happened in the LCL. During the walking, the maximum contact force is 2644N, about 2.99BW, and the maximum ligament tensile force is 595N, whichhappened in the MCL. Our results are consistent with the literature and the model was reliable.