Which muscle is located at the back of the knee?

• A. Sciatic nerve
• B. Anterior scrotal arteries
• C. Popliteus
• D. Peroneal artery

Answer: (C)

The main idea tested here is identifying a muscle that sits at the back of the knee. The popliteus is a small, deep muscle located in the popliteal fossa at the posterior aspect of the knee. It originates from the lateral femoral condyle and inserts on the posterior surface of the tibia above the soleal line. Its job is to unlock the knee by medially rotating the tibia on the femur, which enables the knee to begin flexion from a fully extended position. Because of its precise location and function, it’s the muscle you’d expect to find at the back of the knee. The other options are not muscles in that region: one is a nerve in the thigh that runs near the knee, and the others are arteries, not muscles.