The muscle group whose four heads join one tendon that encloses the kneecap
Quadriceps femoris.
Anatomy · Muscles
Quadriceps femoris
Four-headed extensor of the knee
Lower limb · thigh, anterior compartment
Quadriceps femoris is the great extensor muscle of the front of the thigh, made of four heads: rectus femoris, vastus lateralis, vastus medialis and vastus intermedius. They join in the quadriceps tendon, which surrounds the patella and continues as the patellar ligament to the tibial tuberosity. All four are supplied by the femoral nerve.
How to spot them
- ▸Four heads: rectus femoris in the middle, vastus lateralis outside, vastus medialis inside, vastus intermedius deep
- ▸Common tendon encloses the patella, which lies in it
- ▸The patellar ligament below the patella ends on the tibial tuberosity
- ▸Its tendon tapped just below the kneecap gives the knee jerk
What to know
The knee-jerk reflex, tested with a tendon tap below the patella, tests this muscle group (L3–L4)
Quadriceps femoris — the patellar reflex.
The great extensor of the knee: rectus femoris, vastus lateralis, vastus medialis and vastus intermedius
Quadriceps femoris.
A muscle group supplied by the femoral nerve whose weakness makes stairs and rising from a chair difficult
Quadriceps femoris.
Its heads converge on a tendon that continues as the patellar ligament to the tibial tuberosity
Quadriceps femoris.
Key ideas
- The patella is a sesamoid bone embedded in the quadriceps tendon, increasing the leverage of the muscle.
- Only rectus femoris crosses the hip; the three vasti arise from the femur and act on the knee alone.
Quick-fire facts
- •The four heads: rectus femoris, vastus lateralis, vastus medialis and vastus intermedius.
- •Nerve supply: femoral nerve (L2–L4).
- •All four insert via the quadriceps tendon into the patella, then the patellar ligament to the tibial tuberosity.
- •Main action: knee extension; rectus femoris also flexes the hip.
- •The patella is the largest sesamoid bone in the body.
- •The patellar (knee-jerk) reflex tests the L3–L4 segments.
- •Quadriceps means 'four-headed'; femoris means 'of the thigh'.
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