Which muscle group is responsible for extending the knee joint?

The muscle group that is responsible for extending the knee joint consists of the Rectus Femoris, Vastus Lateralis, Vastus Intermedius, and Vastus Medialis. These four muscles are collectively known as the quadriceps femoris, and they play a crucial role in knee extension.

The Rectus Femoris is unique among the quadriceps as it also aids in hip flexion due to its attachment on the pelvis. The Vastus Lateralis, Vastus Intermedius, and Vastus Medialis are primarily responsible for extending the knee. This extension is essential for activities such as walking, running, and jumping, where the knee must straighten to allow for forward movement and propulsion.

The other options include muscles that do not primarily serve the function of knee extension. For example, the first group features the Biceps Femoris and Semimembranosus, which are involved in knee flexion rather than extension. Similarly, the third option includes Semitendinosus and Gastrocnemius, which also contribute to knee flexion. The last group consists of core muscles that stabilize the trunk and do not affect the knee joint. Therefore, the correct selection highlights the specific muscles directly involved in extending the knee joint.