American Society of Radiologic Technologist (ASRT) Practice Exam

In a lateral projection of the knee, properly flexing the patient's leg to an angle between 20° to 30° is essential for obtaining clear images of the joint. This specific angle allows for optimal visualization of the femoral condyles and the joint space, helping to prevent superimposition and ensuring that important anatomical structures are well-defined. Flexing the leg at this angle also provides a more accurate representation of the knee’s anatomy, facilitating better diagnosis and assessment of any potential issues, such as fractures or joint effusions.

Flexing the knee at angles that are too acute, such as 5° to 10° or too extreme like 90°, may distort the anatomy captured in the X-ray, leading to potential misinterpretation of the images. A flexion of 40° to 45° may also be excessive for a lateral view, hindering the clarity of the joint structures due to increased overlap and foreshortening. Therefore, the accepted and practiced standard for lateral knee projections emphasizes a flexed angle of 20° to 30° for optimal imaging results.