On the mechanical role of intra-articular pressurization in damaged human joints

A large part of world population suffers from degenerative pathologies deriving from the degradation of articular cartilage. It is well established the concurrence to this of synovial disorders, such as inflammation and stiffening, which are sometimes seen as precursors of further cartilage damage. The precise relation of causality between the two phenomena is however still unclear. Whereas proposed models describe the mechanical response of cartilage, they usually neglect the impact of synovial fluid pressurization, considering it as a secondary effect. However, such an assumption may not be always valid, especially in case of deteriorated mechanical properties of the cartilage, such as in arthritis of various kinds. In this paper, we estimate the load-bearing capacity of the whole synovial capsule and its impact to the process. We consider a fluid–solid interaction of the cartilage, intra-articular fluid and synovial membrane by extending a well-known mathematical model of biphasic tissue. Our results show that there is a possible previously neglected beneficial effect arising from the fluid pressurization, particularly important in case of deteriorated cartilage mechanical properties.