When performing a recumbent lateral projection of the knee, the knee should be flexed how many degrees?

When performing a recumbent lateral projection of the knee, the knee should be flexed how many degrees?

• A. 0 degrees
• B. 10 degrees
• C. 20-30 degrees
• D. 40 degrees

Answer: (C)

Positioning the knee with about 20–30 degrees of flexion on a recumbent lateral view is ideal. This amount of bend lets the tibia sit under the femur so the femoral condyles can be superimposed and the joint space remains open, while the patella stays in profile on the side. If the knee is near straight, the bones won’t align true laterally, the condyles won’t superimpose properly, and the joint line can appear distorted. If it’s overly flexed, the tibia tilts and the condyles misalign, which also compromises the true lateral view. The 20–30 degree range therefore provides the clearest, most diagnostic lateral knee image.

Positioning the knee with about 20–30 degrees of flexion on a recumbent lateral view is ideal. This amount of bend lets the tibia sit under the femur so the femoral condyles can be superimposed and the joint space remains open, while the patella stays in profile on the side. If the knee is near straight, the bones won’t align true laterally, the condyles won’t superimpose properly, and the joint line can appear distorted. If it’s overly flexed, the tibia tilts and the condyles misalign, which also compromises the true lateral view. The 20–30 degree range therefore provides the clearest, most diagnostic lateral knee image.