Bones comprise about one-fifth of an individual body weight, with the main functions in supporting and protecting organs, performing movements, and producing the blood cells, among others. Based on the microstructural composition, bones can be classified as cortical bone (compact bone) and trabecular bone (cancellous bone or spongy bone). With reference to Figure 20.1a for a femur long bone, the cortical bone constitutes about 80% of the human skeleton mass and forms an outer layer of bones, while the trabecular bone fills the interior with a porous and cancellous structure; see the microstructure of the femur long bone shown in Figure 20.1b. In general, the cortical bone is stiffer, harder, and denser than the trabecular bone so that it has the ability to protect organs and support the body movement, in addition to its ability to transmit chemical components. In contrast, the trabecular bone has a larger surface area, lower density and stiffness, and higher porosity than those of the cortical bone. Owing to the porous nature of the trabecular bone, there exists space for the blood vessels and bone marrow to flow inside the spongy structure, as can be seen from the computed tomography (CT) scan of the trabecular bone microstructure in Figure 20.2. As such, the bone materials can be characterized as porous media of solid skeleton with the pores filled with fluid. Consequently, the fluid-saturated porous material has been introduced to describe the constitutive behavior of bone materials.Homogenization methods have been introduced to provide a multiscale paradigm for analysis of poroelastic materials, and yield macroscopic balance laws that resemble the Biot's theory [1] while embedding microscopic features [2][3][4]. This work is motivated by the fact that as high-resolution digital imaging techniques emerge, such as the advancement of micro-CT and micro-magnetic resonance imaging (micro-MRI), the investigation of mechanical properties of cortical and trabecular bones can Multiscale Simulations and Mechanics of Biological Materials, First Edition. Edited by Shaofan Li and Dong Qian.