For a lateral knee projection, which of the following flexion angles is correct?

For a lateral knee projection, which of the following flexion angles is correct?

• A. 90 degrees
• B. 5 degrees
• C. 45 degrees
• D. 20 degrees

Answer: (D)

For a lateral knee projection, you want the knee to be flexed only lightly so the femoral condyles can be superimposed and the tibia aligned under the femur. This position keeps the femorotibial joint space open and the patella in profile, producing a true lateral view. About 20 degrees of knee flexion achieves this balance: it places the knee in proper alignment without excessive rotation, giving a clean lateral image with accurate joint visualization. Very little flexion (around 5 degrees) wouldn’t allow true lateral superimposition, and too much flexion (like 45 or more) would alter the relationships and obscure the joint details. A 20-degree bend is the standard that yields the best lateral knee image.

For a lateral knee projection, you want the knee to be flexed only lightly so the femoral condyles can be superimposed and the tibia aligned under the femur. This position keeps the femorotibial joint space open and the patella in profile, producing a true lateral view. About 20 degrees of knee flexion achieves this balance: it places the knee in proper alignment without excessive rotation, giving a clean lateral image with accurate joint visualization. Very little flexion (around 5 degrees) wouldn’t allow true lateral superimposition, and too much flexion (like 45 or more) would alter the relationships and obscure the joint details. A 20-degree bend is the standard that yields the best lateral knee image.