I did my STEAM project on the muscles that are involved in the extension and flexion of the knee. There are many muscles involved but the main muscles on the anterior portion are the rectus femurs, vastus lateralis, vastus medialis, and the vastus intermedius. The vastus intermedius is located deep in the muscles of the quadriceps so they are not visible from this view. The muscles involved in the posterior portion are the biceps femoris, semitendonosus, and the semimembranosus.