What is the primary action of the gracilis muscle at the hip joint?

• A. Lateral rotation of the thigh
• B. Adduction of the thigh
• C. Abduction of the thigh
• D. Extension of the thigh

Answer: (B)

Verified step by step guidance

1. Step 1: Identify the anatomical location and attachments of the gracilis muscle. The gracilis is a long, slender muscle located on the medial (inner) side of the thigh, originating from the pubic bone and inserting on the medial surface of the tibia.
2. Step 2: Understand the general function of muscles located on the medial thigh. Muscles in this region typically act to bring the thigh toward the midline of the body, a movement known as adduction.
3. Step 3: Recall the specific actions of the gracilis muscle. Besides adduction, the gracilis also assists in flexion of the knee and medial rotation of the leg, but its primary action at the hip joint is adduction of the thigh.
4. Step 4: Differentiate adduction from other movements listed in the options: lateral rotation (turning the thigh outward), abduction (moving the thigh away from the midline), and extension (straightening the thigh backward). The gracilis does not primarily perform these actions at the hip.
5. Step 5: Conclude that the primary action of the gracilis muscle at the hip joint is adduction of the thigh, as it pulls the thigh medially toward the body's midline.