Which muscle group is primarily responsible for extending the knee joint?

• A. Quadriceps femoris group
• B. Adductor group of the thigh
• C. Hamstrings group
• D. Gastrocnemius and soleus (triceps surae)

Answer: (A)

Verified step by step guidance

1. Step 1: Understand the action of extending the knee joint, which means straightening the leg at the knee.
2. Step 2: Recall that the quadriceps femoris group is located at the front of the thigh and is the primary muscle group responsible for knee extension.
3. Step 3: Recognize that the hamstrings group, located at the back of the thigh, primarily functions to flex (bend) the knee, not extend it.
4. Step 4: Note that the adductor group mainly functions to bring the thigh toward the midline (adduction) and does not extend the knee.
5. Step 5: Understand that the gastrocnemius and soleus muscles (triceps surae) are primarily involved in plantarflexion of the foot at the ankle, not knee extension.