Why is the femur built as a hollow, thick-walled bone?

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Front and back views of the human skeleton are shown side by side, with labeled bones including the skull, spine, ribs, pelvis, arms, legs, hands, and feet. Insets detail the bones of the foot and hand, highlighting major bone groups and anatomical terms. — human skeleton Front and back views of the human skeleton.

The femur is constructed as a hollow, thick-walled tube because it is specifically adapted to withstand prominent bending, shear, and torsional forces encountered during movement and weight-bearing.1

This tubular configuration, which includes a continuous central cavity known as the medullary cavity, provides an efficient structural design that maximizes rigidity while minimizing the amount of material required. By concentrating the bone tissue in a thick cortex, the femur gains the necessary strength to support the body's weight and act as a lever arm for locomotion. Internally, the bone further optimizes its resistance to stress through the arrangement of trabeculae—a network of intersecting plates and struts that align with major lines of compressive or tensile force.12