What is the best projection to demonstrate the mortise joint?

The oblique ankle projection is the best choice for demonstrating the mortise joint due to its positioning advantage that allows visualization of the joint space between the distal ends of the tibia and fibula. This projection involves rotating the leg and foot approximately 15 to 20 degrees internally, which opens up the mortise joint more clearly than the other projections.

In this position, radiologists can better assess the relationship of the talus within the ankle joint and identify any potential pathologies or injuries. Other projections, such as the anteroposterior ankle or lateral ankle views, either do not adequately display the joint's true anatomy or may obscure important details due to overlapping structures. The AP foot projection focuses on the bones of the foot rather than the ankle joint specifically, making it less useful for evaluating the mortise joint directly. Therefore, the oblique projection is pivotal for accurately assessing this specific area of the ankle.