Where should the central ray be directed for an anteroposterior (AP) projection of the tibia and fibula?

For an anteroposterior (AP) projection of the tibia and fibula, the central ray should be directed to the mid-shaft of the tibia/fibula. This positioning is essential because it allows for an equal representation of both bones within the radiograph, ensuring that important anatomical details are captured effectively. By centering the central ray at the mid-shaft, it accommodates the length of both the tibia and fibula, devoid of distortion, and allows visualization of any fractures or other pathologies present in the mid-portion of these bones.

Directing the central ray at the knee joint or the ankle joint would not provide the necessary focus on the entire length of the tibia and fibula, potentially resulting in missing critical areas of interest, particularly in cases of trauma or during evaluations for other medical conditions. Positioning at the femoral head is also inappropriate, as this is entirely separate from the area of interest being the lower leg bones. Thus, the correct setting at the mid-shaft maximizes diagnostic yield and clarity in assessment.