Rectus Femoris originates from AIIS and assists in which action?

• A. Extending the knee
• B. Flexing the knee
• C. Abducting the hip
• D. Medially rotating the hip

Answer: (A)

Rectus femoris is a biarticular muscle in the quadriceps that crosses both the hip and knee joints. It originates from the AIIS and inserts on the tibial tuberosity via the patellar tendon. Because it crosses the knee joint on the front side, contracting it straightens (extends) the knee. All four quadriceps muscles contribute to knee extension, but this muscle’s primary knee action is extension. It can also assist hip flexion, since it crosses the hip joint, but the action listed here that it most directly accomplishes is extending the knee. The other actions are controlled by different muscles: knee flexion by the hamstrings, hip abduction by the gluteal muscles, and hip medial rotation by various hip rotators.