Which structure is contacted for ALL PI listings?

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

Answer: (B)

For PI listings, the ilium is positioned posteriorly and inferiorly relative to the sacrum, so the contact point must be on the part of the pelvis that represents that posterior-inferior stance. The inferior PSIS sits on the posterior-inferior border of the ilium and provides a stable, easily palpable, and mechanically appropriate contact for delivering the corrective vector in all PI patterns. This landmark allows the thrust to engage the ilium and SI joint in a way that addresses the posterior-inferior rotation consistently.

Sacral base, acetabular ridge, and lateral PSIS do not reliably reflect the posterior-inferior ilium across all PI variations and are used for other patterns or regions, not the PI corrections.