Anatomy Guide › Lower limb
Femur
The femur holds every superlative in the skeleton: longest, heaviest, strongest. Running from hip to knee, it makes up roughly a quarter of your standing height. Its ball-shaped head plugs deep into the hip socket, and from there the bone angles inward down the thigh so that the knees sit under the body's center of gravity — the reason humans can balance on one leg and walk with a smooth gait rather than a side-to-side waddle.
The femur's engineering rewards a close look. The head connects to the shaft by an angled neck, and inside that neck the bone's spongy interior is organized into arching struts aligned precisely along the lines of stress — a pattern so efficient that 19th-century engineers compared it to crane girders. In compression along its axis, a healthy adult femur can bear well over a ton before failing. The great trochanter — the bump you can feel at the side of your hip — is not the hip joint itself but a lever where the gluteal muscles anchor.
The femoral neck is also the skeleton's most consequential weak point. In osteoporotic bone it fractures easily in falls, and 'breaking a hip' almost always means breaking this part of the femur. Because the head's blood supply runs along the neck, these fractures can starve the head of blood, which is why so many are treated with joint replacement rather than repair.
In Anamo, the femur dominates the thigh: quadriceps in front, hamstrings behind, adductors inside, with the femoral vessels and nerve tracking along it. It is the natural first guess of almost any thigh-region round — a long bone gives heat information along its whole length.
- Longest, heaviest, and strongest bone in the body
- Makes up about a quarter of standing height
- Its internal struts align with stress lines like crane girders
- 'Breaking a hip' nearly always means fracturing the femoral neck
Think you could find the femur on a 3D model? Play Anamo and test yourself — every guess is color-coded by how close it lands to the mystery structure.