The Quadriceps are made up of Vastus lateralis, Vastus Intermedius, Vastus Medialis, and Rectus femoris.
The superficial muscles that can be palpated are Vastus Lateralis, Rectus femoris, and Vastus Medialis.
When identifying structures within the knee, there are a few main structures that can be easily palpated. These structures include the patella, the medial and lateral femoral condyles, the medial and lateral tibial condyles, the tibial tuberosity, the fibula, and the medial and lateral collateral ligaments. To learn how to identify these features see the video below.
When the leg is in full extension the roof of the popliteal fossa becomes very taught making it difficult to feel and identify structures inside. When the leg is in a slightly flexed position it becomes easier to move within the structure. The muscular borders that make up the popliteal fossa can be identified and palpated. For a video showing how to identify some of the features of the popliteal fossa and its borders see the video below from (0:35-4:15).