The thigh bone
Femur · os femoris
The longest, strongest bone in your body, running from hip to knee.
What it does
The femur carries your whole body weight every time you stand, walk or climb stairs. Its rounded head sits in a socket in the hip, and its wide lower end forms the top half of the knee joint. Big muscles of the thigh and buttock anchor along its length to swing, lift and straighten your leg.
Surprising fact
Your femur is roughly a quarter of your height, which is why forensic scientists can estimate how tall someone was from a single thigh bone.
Why it matters
A broken femur is a serious injury because the bone is so well protected by muscle that it takes real force to break it. In older people, the narrow neck near the hip is the weak point, which is why a fall can lead to a "broken hip".
Nearby
Read more
Open in the 3D atlas · Suggest a correction · Not medical advice.
3D models: Z-Anatomy & BodyParts3D (CC BY-SA 4.0 / 2.1 JP). Card text CC BY 4.0.