The structure of spongy bone helps reduce the overall weight of bone primarily through its porous, lattice-like design made up of trabeculae. These trabeculae form a lightweight, three-dimensional network with 50–90% of its volume as open space, making spongy bone much less dense than the solid cortical bone. This porous structure minimizes the amount of bone material needed without sacrificing strength, reducing bone mass by 25–40% while still supporting mechanical loads effectively. Spongy bone is strategically located inside bones, especially at the ends and in the interior of flat bones, where it supports stress but avoids adding unnecessary weight. Its trabeculae align with stress lines, optimizing load distribution and further reducing bone weight by cutting down on material needed for strength. The density of spongy bone (0.2–0.8 g/cm³) is significantly lower than that of cortical bone (around 1.8 g/cm³), contributing to a lighter skeleton overall, which aids mobility and reduces energy expenditure during movement. In summary, the high porosity, lattice-like trabeculae framework, strategic placement, and lower density of spongy bone combine to reduce the overall weight of bones while maintaining their strength and functional role in the skeleton.
