Which statement about the mortise projection is true?

Which statement about the mortise projection is true?

• A. Lateral projection of the ankle
• B. AP projection
• C. PA projection
• D. AP oblique projection of the ankle joint

Answer: (D)

Opening the ankle mortise relies on rotating the foot medially to create an AP oblique view. This 15–20 degree medial rotation puts the distal tibiofibular joint (the mortise) in profile and aligns the malleoli so they don’t excessively obscure the joint spaces. With the mortise opened, the fibula sits about midway over the posterior aspect of the tibia and the talus sits snugly between the tibia and fibula, making subtle fractures or widening of the tibiofibular joint easier to detect. That’s why the mortise projection is described as an AP oblique projection of the ankle joint. A lateral view shows the ankle in profile and doesn’t specifically demonstrate the mortise space; a straight AP or PA view would have the malleoli overlapped and the mortise space less visible.

Opening the ankle mortise relies on rotating the foot medially to create an AP oblique view. This 15–20 degree medial rotation puts the distal tibiofibular joint (the mortise) in profile and aligns the malleoli so they don’t excessively obscure the joint spaces. With the mortise opened, the fibula sits about midway over the posterior aspect of the tibia and the talus sits snugly between the tibia and fibula, making subtle fractures or widening of the tibiofibular joint easier to detect.

That’s why the mortise projection is described as an AP oblique projection of the ankle joint. A lateral view shows the ankle in profile and doesn’t specifically demonstrate the mortise space; a straight AP or PA view would have the malleoli overlapped and the mortise space less visible.