Final answer:
The proper rotation of the lower limbs for an AP projection of the pelvis is medial rotation, where the anterior surface of the thigh is aimed toward the midline.
Step-by-step explanation:
For an AP (anteroposterior) projection of the pelvis, the proper rotation of the lower limbs is medial rotation. This type of rotation is when the anterior surface of the thigh moves toward the midline of the body. In the context of radiologic procedures, appropriately positioning the lower limbs ensures clear and diagnostic images. Medial rotation of the femur at the hip joint is necessary to align the femoral necks parallel with the plane of the imaging table to provide an accurate representation of the pelvis and hip joints.