Sacral LOD is:

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

Answer: (C)

Sacral LOD follows the orientation of the sacroiliac joint surfaces, which sit in an oblique plane between the sacrum and ilium. The effective line of drive thus combines a posterior-to-anterior push with a mediolateral component that travels through the joint plane. A purely front-to-back thrust misses the oblique lateral component, a P-A plus vertical (superior-inferior) direction doesn’t align with the joint plane, and a thrust with torque introduces rotation that isn’t needed for engaging the joint surfaces. So the correct description is a posterior-to-anterior line of drive with a mediolateral component through the sacroiliac joint plane.