Why is the central ray directed through the medial malleolus for lateral ankle X-rays?

Directing the central ray through the medial malleolus for lateral ankle X-rays is essential primarily because this location provides an accurate localization of the joint space. Positioning the central ray at the medial malleolus allows for a true lateral projection of the ankle joint, which is crucial for assessing the alignment and condition of the ankle's bony structures and joint spaces.

By centering the beam at this precise anatomical landmark, it enables the radiologist to visualize the tibiotalar joint and surrounding structures effectively. This aids in diagnosing any potential fractures, dislocations, or arthritis present in the ankle area that may be obscured if other projection points were used. Proper localization of the joint space ensures that the most critical aspects of the lateral view are captured in the X-ray image, facilitating clear evaluation and interpretation.