CAMRT Radiography Practice Exam

A radiograph of an AP mortise projection of the ankle shows the lateral joint space is not open. What positioning error likely caused this?

1. Insufficient medial rotation

2. Excessive medial rotation

3. Excessive dorsiflexion of the foot

4. Excessive plantar flexion of the foot

The correct answer is: Excessive medial rotation

The correct answer is that excessive medial rotation likely caused the lateral joint space not to be opened in an AP mortise projection of the ankle. In an AP mortise view, the goal is to visualize the ankle joint, particularly the mortise, which is the space between the talus and the tibia-fibula. Correct positioning involves slightly internally rotating the leg and foot to align the joint space properly. If there is excessive medial rotation, it can close down the lateral aspect of the mortise space, leading to a radiograph where the lateral joint space appears compromised or closed. Understanding the anatomy and mechanics of the ankle joint is crucial in radiographic positioning. Over-rotation alters the alignment needed for a clear visualization of the joint spaces, impacting the diagnostic quality of the image.