A philosophical opinion of creating a model of osmotic component in articular cartilage

Collagen meshwork, proteoglycans and fluid are the three main components in articular cartilage type II. They have been commonly simulated indirectly via Young’s modulus in loads of numerical studies recently in which collagen meshwork and proteoglycans are mainly responsible the dynamic compressive, tensile response and the static (equilibrium) compressive stiffness respectively while fluid plays a significant role of the transient viscoelastic creep and stress-relaxation behavior of the matrix. In this paper, a new approach is presented in which the three components create a 3-D arrangement of interwoven osmotic units. Based on the physical model of the cartilage structure (Broom ND, Marra DL (1985) New structure concepts of articular cartilage demonstrated with a physica model. Connect Tissue Res 14:18 [2]), osmotic units are arranged as the 3D-matrix of voxels i.e. cells including histological information. In order to do so, in this paper, the osmotic configuration with the collagen-proteoglycans entrapment architecture can be represented by the system of balloon-string. Each voxel contains the concentrations of collagen, proteoglycans and water obtained from the histological experiments. Thus osmotic pressure and distension at each osmotic unit can be computed based on these concentrations. This simulation allows to setup a new model of articular cartilage in which fluid flow is described and calculated without physical formulas, that is able to probe and study fluid and associated matrix pressures and deliver insight into the advection of pressures, diffusion and exudation of fluid, and solutes within loaded cartilage. Therefore, a new model of articular cartilage is ready to create based on the new approach of the osmotic component