Which action is performed by the rectus femoris muscle?

Which action is performed by the rectus femoris muscle?

• A. Extend knee
• B. Flex the knee
• C. Abduct the thigh
• D. Adduct the thigh

Answer: (A)

Rectus femoris is part of the quadriceps and crosses both the hip and knee joints. When it contracts, it pulls on the quadriceps tendon and patellar ligament, transmitting force to the tibial tuberosity to straighten the knee—so it extends the knee. Although it can assist with hip flexion because it crosses the hip joint, its well-known and primary action at the knee is extension. It does not abduct or adduct the thigh (that’s done by other muscles) and it does not flex the knee (that movement is produced by the hamstrings and other knee flexors).

Rectus femoris is part of the quadriceps and crosses both the hip and knee joints. When it contracts, it pulls on the quadriceps tendon and patellar ligament, transmitting force to the tibial tuberosity to straighten the knee—so it extends the knee. Although it can assist with hip flexion because it crosses the hip joint, its well-known and primary action at the knee is extension. It does not abduct or adduct the thigh (that’s done by other muscles) and it does not flex the knee (that movement is produced by the hamstrings and other knee flexors).