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

关节软骨和半月板对膝关节的正常机械功能至关重要。这些软组织由65-80%的液体组成。在日常活动中，膝关节受到挤压会引起这些组织的液体流动。软骨代谢也受到滑液的调节，滑液为软骨细胞带来营养。此外，流体压力可以支撑超过50%的膝关节负荷。因此，为了了解正常的膝关节力学功能，有必要充分发现软骨和半月板中流体压力和流动的力学和生物学功能。目前，由于在膝关节内流体压力测量和膝关节解剖准确模型的流体压力预测方面存在困难，这方面的信息非常有限。***我们最近开始研究软骨和半月板流体压力和流动的建模。我们的膝关节模型是基于从人类受试者获得的磁共振成像构建的。通过全面的数学模拟，阐明了膝关节在流体压力和流量调节下的力学作用。所提出的研究将促进对人类膝关节机械功能的理解，使其与生理更相关。这些方法和结果将通过动物关节的力学和生物学测试进行验证，并将通过一种充分利用计算机建模和人体高分辨率成像的创新方法在人类膝盖上进一步探索结果。我们将(1)评估人体膝关节在流体压力调节下的负荷支撑机制，(2)发现流体压力和流量在猪膝关节软骨代谢中的作用，(3)应用验证的方法预测人类站立和行走的膝关节力学。这些研究将充分利用我们在膝关节建模方面的最新进展和卡尔加里大学现有的最先进的设施来推进关节的接触力学。本研究的预期结果包括进一步了解膝关节力学功能的基本过程，以及可用于预测个体特定膝关节力学的综合计算机方法。***我们的验证方法和新结果可用于生物工程的进一步发展。一个完善的膝关节模型可以在未来的研究中进一步用于预测随着年龄增长而退化的机械功能。机械调节软骨代谢的知识，一旦扩展到人类膝关节软骨，可能最终用于设计运动策略，以减缓软骨的衰老过程。鲁棒关节模型也可用于其他应用，如机械和机器人系统的仿生设计。这项研究将吸引有前途的年轻研究人员到加拿大工作。

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.