Which listing produces inferior SI edema?

• A. PI
• B. AS
• C. EX
• D. IN

Answer: (B)

Inferior sacroiliac edema reflects a loading pattern where the inferior part of the SI joint is stressed due to the orientation of the innominate relative to the sacrum. An anterior-superior (AS) ilial position places the ilium forward and slightly up, which concentrates joint stress at the inferior portion of the SI articulation. That focused stress can lead to edema in the inferior SI region on imaging. The other listings describe different directions of ilial/sacral alignment that tend to load other parts of the SI joint, so they are less likely to produce edema specifically in the inferior area.