Which description describes the sacral line of drive for sacral P-L/P-R includes an anterior-posterior component and medial-lateral through the joint plane?

• A. P-A, S-I
• B. P-A only
• C. P-A, I-S
• D. P-A, M-L through joint plane

Answer: (D)

The line of drive for sacral P-L/P-R is defined by both a posterior-to-anterior component and a medial-to-lateral component that travels through the sacroiliac joint plane. Delivering the thrust in this combined direction matches how the sacral base moves relative to the ilium, engaging the joint plane obliquely to produce the desired motion at the SI joints. A pure anterior-posterior push would miss the necessary side-to-side alignment with the joint plane, and a drive that lacks the through-the-joint-plane element wouldn’t optimally engage the SI articulation. Therefore, the correct description is a posterior-to-anterior component with a medial-to-lateral component through the joint plane.