Which list correctly names the muscles that comprise the quadriceps for knee extension?

Which list correctly names the muscles that comprise the quadriceps for knee extension?

• A. Rectus femoris, Vastus intermedius, Vastus medialis, Vastus lateralis
• B. Biceps femoris, Semitendinosus, Semimembranosus
• C. Tibialis anterior
• D. Rectus femoris, Vastus intermedius, Vastus medialis, Vastus lateralis

Answer: (D)

Knee extension is produced by the quadriceps femoris, a four-part muscle group. Those four muscles are rectus femoris and the three vastus muscles—medialis, intermedius, and lateralis. They converge into the quadriceps tendon, which attaches to the patella and then to the tibial tuberosity, generating the straightening motion when they contract. The set that includes rectus femoris and all three vastus muscles matches this group exactly, so it correctly names the knee extensor muscles. Other options include muscles that don’t extend the knee—like the hamstrings, which flex the knee and extend the hip, or tibialis anterior, which moves the ankle—so they don’t name the knee extensors.

Knee extension is produced by the quadriceps femoris, a four-part muscle group. Those four muscles are rectus femoris and the three vastus muscles—medialis, intermedius, and lateralis. They converge into the quadriceps tendon, which attaches to the patella and then to the tibial tuberosity, generating the straightening motion when they contract. The set that includes rectus femoris and all three vastus muscles matches this group exactly, so it correctly names the knee extensor muscles. Other options include muscles that don’t extend the knee—like the hamstrings, which flex the knee and extend the hip, or tibialis anterior, which moves the ankle—so they don’t name the knee extensors.