Fibrocartilage

Abstract

The human menisci and intervertebral discs perform several important mechanical functions in the human body. The ability to perform these functions and consequently their intrinsic biomechanical properties are dependent on the interaction of the constituents of these structures. Both the menisci and intervertebral discs have a fibrocartilaginous structure that consists of two distinct phases: a fluid phase consisting of mainly water and dissolved electrolytes, and a solid phase composed of highly oriented collagen fibers, cells, proteoglycans and other proteins. As with all other biological materials, both menisci and discs exhibit non-linear viscoelastic and anisotropic properties. The non-linear stiffness or elasticity of the structure is imparted by the collagen fibers and to a lesser extent by osmotic pressures within the tissue which are generated by the degree of hydration [1, 2]. The viscoelastic or energy dissipation properties are a result of fluid flow within and through the structures and also of molecular relaxation effects from the motion of long chains of collagen and proteoglycans [3]. Anisotropy is a consequence of the orientation and concentration of collagen fibers within the proteoglycan gel.