Which muscle is NOT a quadriceps muscle?

• A. Sartorius
• B. Rectus femoris
• C. Vastus medialis
• D. Vastus intermedius

Answer: (A)

The main idea is that the quadriceps femoris is a four-muscle group whose primary role is to extend the knee. Those four muscles are rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius, and they all converge into a common quadriceps tendon that attaches to the patella and then to the tibia. The muscle that is not part of this group is the sartorius. Sartorius runs from the hip to the medial tibia, crosses both the hip and knee joints, and helps with hip flexion, abduction, and external rotation, plus assisting knee flexion when the hip is flexed. Because it doesn’t extend the knee and doesn’t share the quadriceps tendon arrangement, it is not a quadriceps muscle.