Finite element analyses for time-dependent and depth-dependent deformation of articular cartilage and chondrocytes under constant compression

Human joints are capable of functioning effectively with low friction and without failure throughout human life under circumstances where both articular cartilage as bearing material and synovial fluids as lubricants fulfill their normal functions. It is well accepted that articular cartilage adapts to changing mechanical environments. As the rubbring condition is getting severe, the articular cartilage will be worn, resulting in osteoarthritis, but little is known about the mechanism to osteoarthritis. It is important to clear the stress-strain state of cartilage and in chondrocytes under repeated cartilage deformation to know how osteoarthritis gets to start and progress. The purpose of this study is to investigate an influence of chondrocytes on stress-strain state of articular cartilage and an influence of position of chondrocytes on its depth-dependent deformation. FEM analyses predict that the time-dependent and depth-dependent deformation of articular cartilage is caused by fluid exudation, but material properties of chondrocytes do not affect the bulk deformation of articular cartilage so much. The deformation of chondrocytes is depth-dependent and the largest time-dependent deformation behavior occurs in the surface layer. These results may clear how the transduction of mechanical stimuli concern about metabolism of articular cartilage via chondrocytes.