The origin of SI pain is very rarely the SI joint. If you have had SI blocks without 2-3 hours or temporary relief immediately after the injection, the SI joint is not the cause of your pain. Typically, SI joint pain originates from the disc or nerve root at L4-5 or L5-S1. I have however seen three cases of pain originating from the transverse-alar articulation at L5-S1.
This articulation is also known as sacralization of the L5-S1 level. What this structure really is turns out to be an enlarged transverse process of L5 that creates a new joint with the ala of the sacrum on that side (hence: tranverse-alar articulation).
To discover the source of your pain, you need diagnostic blocks of all of the potential pain provoking structures. You need to keep a pain diary (see section on pain diary on the website). Once the suspect structure is anesthetized and is the obvious source of pain, then if needed, a surgical plan can be established.
Donald Corenman, MD, DC is a highly-regarded spine surgeon, considered an expert in the area of neck and back pain. Trained as both a Medical Doctor and Doctor of Chiropractic, Dr. Corenman earned academic appointments as Clinical Assistant Professor and Assistant Professor of Orthopaedic Surgery at the University of Colorado Health Sciences Center, and his research on spine surgery and rehabilitation has resulted in the publication of multiple peer-reviewed articles and two books.