Mechanics of Knee Joints - The Role of Fluid Pressure and Flow in Load Sharing and Cartilage Metabolism

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Articular cartilage and meniscus are essential for the normal mechanical function of the knee joint. These soft tissues are comprised of 65-80% fluid. Fluid flow is induced in these tissues by knee compressions during daily activities. Cartilage metabolism is also regulated by the synovial fluid, which brings nutrients to cartilage cells. Furthermore, fluid pressure can support over 50% of the knee load. Therefore, it is necessary to fully discover the mechanical and biological functions of fluid pressure and flow in cartilage and meniscus in order to understand normal knee mechanical functions. Currently, this information is very limited due to difficulties in both fluid pressure measurements inside the knee and fluid pressure predictions with an anatomically accurate model of the knee joint.***       We have recently initiated research into the modeling of cartilage and meniscus fluid pressure and flow. Our knee models are constructed based on magnetic resonance imaging obtained from human subjects. Comprehensive mathematical simulation is performed to elucidate the mechanical function of the knee regulated by the fluid pressure and flow. The proposed research will advance the understanding of mechanical functions of human knee joints to a level with more physiological relevance. The approaches and results will be validated through mechanical and biological tests on animal joints, and the results will be further explored in human knees through an innovative approach that takes full advantage of both computer modeling and high-resolution imaging on human subjects. We will (1) assess the load support mechanism of the human knee regulated by the fluid pressure, (2) discover the role of fluid pressure and flow in the cartilage metabolism of the pig knee, and (3) apply the validated approach to predict the knee mechanics of human standing and walking. These studies will fully use our recent progress in the modeling of the knee joint and existing state-of-the-art facilities at the University of Calgary to advance the contact mechanics of the joint. Expected outcomes from this research include further understanding of fundamental processes in knee joint mechanical functions and a comprehensive computer approach that can be used to predict subject-specific knee mechanics for individuals.***       Our validated approach and new results may be used in further developments in bioengineering. A well-established knee model can be further used in future studies to predict degenerated mechanical functions with aging. Knowledge of mechanically regulated cartilage metabolism, once it has been extended to human knee cartilage, may eventually be used to design exercise strategies to slow down the aging process in cartilage. A robust joint model could also be used in other applications, such as biomimetic design of mechanical and robotic systems. The research will attract promising young researchers to work in Canada.