In the PA tangential projection of the patella, the CR is directed at what angle?

• A. 0°
• B. 15° cephalic
• C. 30° caudal
• D. 45° cephalic

Answer: (D)

In the PA tangential projection of the patella, the central ray (CR) is directed at a cephalic angle of 45 degrees. This specific angle is crucial as it helps to maximize the visualization of the patella while minimizing superimposition over the femur and other structures, thereby enhancing diagnostic clarity. The cephalic angle elevates the central ray in relation to the film or image receptor, which is particularly important in obtaining an unobstructed view of the patellar contours and its relationship with the femur.

The positioning allows for optimal visualization of the patella in relation to the knee joint, as the perpendicular position would not adequately open or define the joint space. The proper angling assists in reducing the likelihood of distortion and aids in the interpretation of potential pathologies related to the patella and surrounding anatomical structures.