Which projection is commonly used to tangentially image the patellofemoral joint with the knee flexed and the patient is able to be seated or supine?

Which projection is commonly used to tangentially image the patellofemoral joint with the knee flexed and the patient is able to be seated or supine?

• A. Settegast
• B. Beclare
• C. Merchant method
• D. Holmblad

Answer: (C)

Tangential imaging of the patellofemoral joint with the knee flexed relies on a projection that places the patellar articulation in true profile while the joint is opened. The Merchant method achieves this by positioning the patient supine or seated with both knees flexed about 40 degrees and supported so the knees stay at that angle; the x-ray beam is directed horizontally to the midline, producing a true tangential view of the patellofemoral joint. This setup minimizes superimposition and reveals the articular surfaces, making it ideal for assessing patellar tilt, subluxation, and congruence within the femoral trochlear groove. Other methods change the knee angle or project through different knee structures: for instance, Settegast uses deep knee flexion and a different orientation, Holmblad targets the intercondylar fossa with an axial projection, and Beclere offers another tangential variant with distinct positioning. So the projection described is the Merchant method.

Tangential imaging of the patellofemoral joint with the knee flexed relies on a projection that places the patellar articulation in true profile while the joint is opened. The Merchant method achieves this by positioning the patient supine or seated with both knees flexed about 40 degrees and supported so the knees stay at that angle; the x-ray beam is directed horizontally to the midline, producing a true tangential view of the patellofemoral joint. This setup minimizes superimposition and reveals the articular surfaces, making it ideal for assessing patellar tilt, subluxation, and congruence within the femoral trochlear groove. Other methods change the knee angle or project through different knee structures: for instance, Settegast uses deep knee flexion and a different orientation, Holmblad targets the intercondylar fossa with an axial projection, and Beclere offers another tangential variant with distinct positioning. So the projection described is the Merchant method.