<p>The objective of this study is to design and develop biomimetic hierarchical nanocomposites composed of hydroxyapatite (HAp) and polylactic acid as alternative materials for implants and scaffolds in femur and tibia bones. The study aims to identify the most suitable composition capable of withstanding the loads experienced by scaffolds in the human body, effectively replacing damaged or fractured bones. Multiple material compositions with varying weight percentages were explored to determine the most effective formulation, revealing that hierarchically structured composites are optimal for bio-implant materials. Finite element analysis (FEA) was conducted on femur and tibia bones using both biomimetic hierarchical nanocomposites and non-hierarchical nanocomposites under various loading conditions such as standing, walking, running, and jumping. Different isotropic material properties were designed using a material designer tool and applied to the geometries for analysis. The performance of isotropically structured femur and tibia bones was compared with hierarchically structured femur and tibia bones, along with isotropic tensile samples and hierarchically structured tensile samples. The results of the FEA analysis revealed that von Mises stress–strain values and total deformation were significantly improved in the hierarchically structured geometries of femur, tibia, and tensile samples compared to their isotropic counterparts.</p>