ALL PI listings contact which structure?

• A. Sacral base
• B. Inferior PSIS
• C. Acetabular ridge
• D. Lateral PSIS

Answer: (B)

A PI listing reflects a posterior-inferior position of the ilium relative to the sacrum, so the contact point is chosen to engage that specific area with the correct vector. The inferior PSIS sits at the lower, back corner of the ilium and is right beside the SI joint, making it the most stable and effective point to apply a thrust that moves the ilium anteriorly and superiorly to correct the posterior-inferior orientation.

The other structures aren’t aligned with the typical correction path for a PI listing: contacting the sacral base would target the sacrum itself rather than the ilium, the acetabular ridge is deep in the hip socket and not the correct lever for this adjustment, and the lateral PSIS doesn’t provide the same direct access to the SI joint needed to address a PI misalignment.