Which muscle is the primary extensor of the thigh at the hip joint?

• A. Gluteus maximus
• B. Gluteus medius
• C. Rectus femoris
• D. Iliopsoas

Answer: (A)

Verified step by step guidance

1. Understand the action described: extension of the thigh at the hip joint means moving the thigh backward, increasing the angle between the front of the thigh and the pelvis.
2. Recall the main muscles involved in hip movements: the gluteus maximus, gluteus medius, rectus femoris, and iliopsoas all have roles around the hip joint but differ in their primary actions.
3. Identify the function of each muscle: the gluteus maximus is known for powerful hip extension; the gluteus medius primarily abducts the thigh; the rectus femoris mainly extends the knee and flexes the hip; the iliopsoas is a strong hip flexor.
4. Conclude that since the question asks for the primary extensor of the thigh at the hip, the muscle responsible for this action is the gluteus maximus.
5. Remember that understanding muscle origin, insertion, and action helps in identifying their primary functions in joint movements.