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

• A. Hip adductor group
• B. Quadriceps femoris group
• C. Hamstring group
• D. Triceps surae (gastrocnemius and soleus)

Answer: (B)

Verified step by step guidance

1. Step 1: Understand the movement involved - knee extension refers to straightening the leg at the knee joint, increasing the angle between the thigh and the lower leg.
2. Step 2: Identify the primary muscles responsible for knee extension. The quadriceps femoris group, located at the front of the thigh, is the main muscle group that extends the knee.
3. Step 3: Recognize the role of other muscle groups listed: the hamstring group primarily flexes the knee, the hip adductor group mainly moves the thigh toward the body's midline, and the triceps surae (gastrocnemius and soleus) primarily plantarflex the foot at the ankle.
4. Step 4: Confirm that the quadriceps femoris group consists of four muscles (rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius) that work together to extend the knee joint.
5. Step 5: Conclude that the quadriceps femoris group is the correct answer because it is the primary muscle group responsible for knee extension.