Bones Biomechanics

Bones are anisotropic but are approximately transversely isotropic. In other words, bones are stronger along one axis than across that axis, and are approximately the same strength no matter how they are rotated around that axis.

The stress-strain relations of bones can be modeled using Hooke's law, in which they are related by elastic moduli, e.g. Young's modulus, Poisson's ratio or the Lamé parameters. The constitutive matrix, a fourth order tensor, depends on the isotropy of the bone.
σij = Cijklεkl


HOOKE's LAW
Hooke's law of elasticity is an approximation that states that the amount by which a material body is deformed (the strain) is linearly related to the force causing the deformation (the stress).