A patient comes to radiology with chondromalacia of the patella. What projection should be performed to best demonstrate the femoropatellar joint space?

The Merchant method, which is a specific radiographic projection, is particularly useful for visualizing the femoropatellar joint space. This method allows for the assessment of the patellofemoral joint by placing the patient in a seated position with the knees flexed at 45 degrees. This positioning opens up the joint space, making it easier to see any abnormalities, such as those found in chondromalacia of the patella. The Merchant view provides a clear image of the relationship between the patella and the femur, as well as any potential joint space narrowing or irregularities in cartilage.

In contrast, other projections may not adequately demonstrate the joint space. The sunrise view is beneficial for visualizing the patella but does not provide the comprehensive view of the joint space that the Merchant method does. The AP view typically gives a general overview of the knee joint but can obscure the details of the femoropatellar joint due to superimposition. The lateral view can provide valuable information about the overall alignment and condition of the knee but is less focused on the patellofemoral joint compared to the Merchant method. Therefore, for assessing chondromalacia, the Merchant method is the optimal choice.