During a lateral knee radiograph, how should the knee be rotated relative to the film to achieve the intercondylar line perpendicular to the film?

During a lateral knee radiograph, how should the knee be rotated relative to the film to achieve the intercondylar line perpendicular to the film?

• A. The knee is rotated laterally so that the intercondylar line is perpendicular to the film.
• B. The knee is rotated medially so that the intercondylar line is parallel to the film.
• C. The knee is extended fully with the medial portion of the knee touching the film.
• D. The knee is rotated to prone position so that the patella is touching the film.

Answer: (A)

The key idea is to position the knee so the posterior aspects of the femoral condyles sit in the same plane as the image receptor, giving a true lateral view. Rotating the leg laterally (external rotation) aligns the intercondylar line so it is perpendicular to the film, which allows the femoral condyles to be superimposed and the intercondylar notch to be seen without distortion. If you rotate the knee medially, that line becomes oblique to the film and the condyles won’t be superimposed, compromising the lateral projection. Extending fully with the medial knee touching the film would create an AP-like view rather than a true lateral, and placing the knee prone with the patella touching the film also changes the projection away from a lateral knee.

The key idea is to position the knee so the posterior aspects of the femoral condyles sit in the same plane as the image receptor, giving a true lateral view. Rotating the leg laterally (external rotation) aligns the intercondylar line so it is perpendicular to the film, which allows the femoral condyles to be superimposed and the intercondylar notch to be seen without distortion. If you rotate the knee medially, that line becomes oblique to the film and the condyles won’t be superimposed, compromising the lateral projection. Extending fully with the medial knee touching the film would create an AP-like view rather than a true lateral, and placing the knee prone with the patella touching the film also changes the projection away from a lateral knee.