Which term describes rotation toward the midline of the body?

• A. External rotation
• B. Internal rotation
• C. Protraction
• D. Retraction

Answer: (B)

Rotation toward the midline is called internal rotation, also known as medial rotation. It happens at joints like the shoulder and hip when a limb turns so its front surface moves closer to the center of the body. For example, turning the thigh so the knee points inward toward the other leg or rotating the arm at the shoulder so the elbow moves inward demonstrates internal rotation. The opposite movement—rotation away from the midline—is external rotation. Protraction and retraction describe sliding movements of a part forward or backward in a plane (such as the shoulder blades), not twisting around an axis, so they don’t describe rotation toward the midline.