Which of the following examinations is least likely to require the use of a grid for an adult patient?

The knee examination is least likely to require the use of a grid for an adult patient primarily due to the anatomy and the typical imaging techniques involved. Grids are employed in radiography to reduce the amount of scattered radiation that reaches the film or detector, enhancing image quality, particularly for thicker body parts or those with higher levels of soft tissue.

In the case of the knee, the area being imaged is relatively small and not extremely thick compared to other areas such as the abdomen or lumbar spine. The knee joint can be effectively visualized without the additional complexity introduced by a grid, which is usually utilized for larger or denser areas to improve diagnostic clarity.

Other examinations like the hip, abdomen, and lumbar spine often involve greater tissue thickness and are more prone to scatter radiation, making the grid a necessary tool for achieving optimal image quality in these regions. As a result, the knee is typically imaged without a grid, leading to straightforward and adequate results with less technical complication.