Which muscle group is primarily responsible for extension of the knee joint?

• A. Quadriceps femoris
• B. Iliopsoas
• C. Gastrocnemius
• D. Hamstrings

Answer: (A)

Verified step by step guidance

1. Step 1: Understand the movement involved. Knee extension refers to the straightening of the knee joint, increasing the angle between the thigh and the lower leg.
2. Step 2: Identify the muscle groups involved in knee movement. The main muscle groups acting on the knee are the quadriceps femoris, hamstrings, gastrocnemius, and iliopsoas.
3. Step 3: Recall the primary function of each muscle group: the quadriceps femoris is known for extending the knee; the hamstrings primarily flex the knee; the gastrocnemius assists in plantar flexion of the foot and also flexes the knee; the iliopsoas is mainly involved in hip flexion.
4. Step 4: Match the muscle group to the action of knee extension. Since the quadriceps femoris is the main muscle responsible for straightening the knee, it is the primary extensor of the knee joint.
5. Step 5: Conclude that the quadriceps femoris is the correct answer for the muscle group primarily responsible for knee extension.