CAMRT Radiography Practice Exam

The degree of angulation for an ASIS to table top distance of 25 cm and above for an AP knee is:

1. Perpendicular

2. 5 - 10 degrees caudad

3. 3 - 5 degrees cephalad

4. 15 - 20 degrees cephalad

The correct answer is: 3 - 5 degrees cephalad

In the context of radiographic positioning for an AP (Anteroposterior) knee projection, the degree of tube angulation is crucial to obtaining a clear diagnostic image of the knee joint. When the distance from the ASIS (Anterior Superior Iliac Spine) to the tabletop reaches 25 cm or more, it is necessary to apply a specific angulation to compensate for the anatomical positioning of the femur and the alignment of the knee joint. When angling the tube, if the ASIS-to-tabletop distance is 25 cm or greater, an angulation of 3 to 5 degrees cephalad is generally recommended. This slight angle is designed to ensure that the central ray intersects the knee joint accurately, thereby helping to produce an optimal image of the anatomical structures—including the femur, patella, and tibia—without causing distortion. The cephalad angle allows the beam to project more directly onto the structures being imaged. Understanding this technique is essential for radiographers, as obtaining a well-positioned image can significantly impact the diagnosis and subsequent treatment of knee conditions. The correct angulation accommodates the natural curvature of the knee joint, which helps to ensure the clarity and quality of the radiographic image.