Which zygapophyseal (facet) joints are demonstrated on the AP oblique projection of the lumbar spine?

In the AP oblique projection of the lumbar spine, the facet joints demonstrated are those closest to the image receptor (IR). This positioning allows for an unobstructed view of the zygapophyseal joints on the side that is facing the IR. By angling the patient correctly (typically at 45 degrees), the practitioner can visualize the joints more clearly.

This technique is particularly effective because it reduces superimposition of the vertebrae and allows the radiograph to capture the joint surfaces in profile. The structure and orientation of the lumbar spine emphasize the visibility of the joints closest to the IR due to the angulation of the x-ray beam. Hence, the correct answer highlights the importance of positioning in radiography, ensuring that the pertinent anatomy is accurately assessed for diagnostic purposes.