The most common reason for a hip replacement is the wear of the cartilage in natural joints (osteoarthritis). During everyday movement, tangential loading of the joint can slowly wear the cartilage or lead to surface cracks. However, studies have shown that the cartilage can also regenerate itself, if the cells are supplied with nutrients. These nutrients are carried by the synovial fluid which can diffuse in the porous cartilage if a pressure gradient is present. It is assumed that oscillations in the normal loading of the joint have a pump effect on the synovial fluid that is beneficial for nutrient supply and, hence, cartilage regeneration.

A thorough understanding of the mechanisms that cause wear and promote regeneration can lead to the development of new, more conservative therapies in the earlier stages of osteoarthritis and may thus help to avoid the often unsatisfactory and expensive joint replacement.
This highly interdisciplinary research area combining contact mechanics, biology and fluid mechanics is very young and the research work at the Department of System Dynamics and Friction Physics is just at the beginning. Our current work is focused on the theoretical modeling of the contact problem and the coupled diffusion problem including wear and growth laws based on the stress distributions inside the cartilage. Thereby the cartilage mechanics considering the porous and viscoelastic solid phase as well as the fluid phase of the biphasic material is especially challenging.

Basics of contact mechanics of biological tissues, in particular articular cartilage, are described in the book written by guest professor of our Department, I. Argatov, and professor of the Aberystwith University, G. Mishuris, Indentation Testing of Biological Materials, Springer, 2018:

www.springer.com/de/book/9783319785325 [2]