Question

For an AP projection of the knee on a patient whose measurement from ASIS to tabletop is 21 cm, which CR direction will best demonstrate the knee joint? a) 5 degrees caudad b) 10 degrees caudad c) 5 degrees cephalad d) 0 degrees (perpendicular)

Answer 1

For the AP projection of the knee with a 21 cm distance from ASIS to tabletop, a 5 degrees caudad CR angle is recommended to best visualize the knee joint. (Option a)

Step-by-step explanation:

For an AP projection of the knee on a patient whose measurement from ASIS to tabletop is 21 cm, the proper central ray (CR) direction to best demonstrate the knee joint would be 5 degrees caudad. This is because the angle compensates for the natural inclination of the femur due to the width of the hips compared to the knee. By directing the ray caudad, or downward, it aligns with the axis of the femur and the knee joint space, ensuring that the joint is properly visualized on the radiographic image.

This strategic angulation of the central ray optimizes the imaging process by minimizing foreshortening and enhancing the clarity of anatomical structures in the knee joint, providing diagnostically valuable information for healthcare professionals.