Bone is abundant in extracellular matrices, and therefore,"bone quality" appears to reflect the property of the bone matrix. The bone matrix is composed of minerals and organic materials. The volume of collagen fiber is approximately 90% of the whole organic materials of the bone matrix. Since collagen fibers could resist tension, the elasticity of the bone seems to come from the property of the collagen fibers. The mineralization of the bone matrix is achieved by the formation of hydroxyapatite crystals. The non-collagenous proteins and proteoglycans may regulate the growth of the mineralized crystal.