|Derivation||The vast muscle on the lateral side of the thigh.|
|Origin||Front surface on the upper end of the femur. The belly wraps around the lateral side of the femur and attaches to a long line on the back.|
|Action||Straightens the leg at the knee.|
Vastus lateralis is a wide muscle. Its ends lie forward on the thigh, but its middle extends across most of the lateral side.
It lies under the whole of the iliotibial band, and a break may be seen at its forward edge.