The Thigh Engine
The four muscles that straighten your knee
The quadriceps is the biggest muscle group in your body â four muscles at the front of your thigh that team up to straighten your knee every time you stand, kick, or jump.
The four quadriceps muscles
Real anatomy photo spot: rectus femoris, vastus lateralis, vastus medialis, vastus intermedius
Meet the four engines
Rectus femoris â The Up-Front Engine
Runs straight down the middle of the thigh. The only one of the four that also crosses the hip, so it helps lift your leg forward too.
One cable, one job
All four muscles join into one tendon, which wraps around the patella and attaches to a bump on your tibia called the tibial tuberosity. When the quadriceps pulls, your knee straightens. It's your standing, stepping, kicking and jumping muscle â your body's main thigh engine.
Mr. Bones says: I'm a fictional skeleton, not a doctor! This is for learning and fun. If anything hurts, stop and tell a grown-up you trust.
