The quadriceps femoris muscle group (rectus femoris, vastus lateralis, vastus medius, and vastus intermedius) crosses the knee via the patella and acts to extend the leg. The hamstring group muscles (semitendinosus, semimembranosus, and biceps femoris) flex the knee and extend the hip.

Are quadriceps flexor or extensor?

The quadriceps femoris is a hip flexor and a knee extensor. It consists of four individual muscles; three vastus muscles and the rectus femoris. They form the main bulk of the thigh, and collectively are one of the most powerful muscles in the body. It is located in the anterior compartment of the thigh.

Does the quadriceps femoris flex or extend the leg?

The function of the quadriceps femoris muscle is to extend the leg at the knee joint and to flex the thigh at the hip joint.