The rectus femoris covers the vastus intermedius, so you can only see the rectus femoris, vastus lateralis, and vastus medialis. (best-leg-exercises.com)
Muscles producing joint actions at the knee joint are the quadriceps muscles (vastus medialis, vastus lateralis, vastus intermedius and rectus femoris at the front, with the hamstring muscles (semitendinosis, semimembranosus and biceps femoris) at the back along with the popliteus muscle. (sportsinjuryclinic.net)
The Quadriceps are group of 4 muscles in the front of the thigh — vastus lateralis, vastus intermedius, vastus medialis, and the rectus femoris. (best-leg-exercises.com)