What is the best initial treatment for low back pain originating from the sacroiliac (SI) joint?

Initial Treatment for Sacroiliac Joint Low Back Pain

For low back pain originating from the SI joint, begin with physical therapy focused on pelvic stabilization exercises combined with NSAIDs, reserving diagnostic injections and interventional procedures for patients who fail conservative management after 3-6 months. 1, 2

Diagnostic Confirmation Before Treatment

Before initiating treatment, confirm SI joint as the pain generator:

• Perform at least 3 positive provocative maneuvers (thigh thrust, FABER's test, lateral compression, Gaenslen's test, distraction test) to achieve 94% sensitivity and 78% specificity for SI joint pain 1, 3
• Obtain plain radiographs of the SI joints and spine first (rated 9/9 "usually appropriate" by ACR) to assess for structural changes and rule out other pathology 4, 1
• If radiographs are negative or equivocal and inflammatory disease is suspected (age <45, morning stiffness >3 months, improvement with exercise, alternating buttock pain), proceed to MRI SI joints without contrast (rated 8/9) with fat-suppressed sequences (T2-weighted fat-suppressed or STIR) 4, 1

First-Line Conservative Treatment (3-6 Months)

Conservative management should be implemented first for patients with moderate SI joint pain, symptom duration <6 months, or those not surgical candidates 5, 2:

• Physical therapy with pelvic stabilization exercises specifically targeting the SI joint 1, 3
• NSAIDs taken regularly once diagnosis is established 4, 6
• SI belt for activity modification 6
• Manual therapy and biomechanical correction for mechanical SI joint dysfunction 3

The evidence strongly supports this multimodal conservative approach as initial therapy, with interventional procedures reserved for treatment failures 2, 6.

Second-Line Interventional Options (After Conservative Failure)

If conservative treatment fails after 3-6 months:

Therapeutic Injections

• Corticosteroid injections (intra-articular or peri-articular) can provide >3 months relief in some patients 1, 2
• Peri-articular injections may be superior (100% response) compared to intra-articular alone (36%) when extra-articular pain contributions exist 1
• Prolotherapy with dextrose demonstrates superior results (64% achieving 50% pain relief at 6 months) compared to corticosteroid injections (27%) 1, 3

Radiofrequency Ablation

• Conventional or thermal radiofrequency ablation of medial branch nerves should be performed for low back pain when previous diagnostic injections provided temporary relief 4
• Cooled radiofrequency ablation may be used for chronic SI joint pain, with extensive lesioning strategies (L5 dorsal ramus and S1-3 lateral branches) demonstrating strongest evidence 4, 2

Important caveat: The diagnostic value of SI joint infiltration remains controversial due to potential false-positive and false-negative results 2. Single diagnostic blocks are insufficient—dual comparative blocks with >70-80% concordant pain relief are required before considering surgical intervention 1.

Third-Line Surgical Consideration

SI joint fusion should only be considered if ALL criteria are met 1:

• ≥3 positive provocative maneuvers
• Dual diagnostic blocks with >70-80% concordant pain relief
• Radiographic evidence of SI joint degeneration
• Failure of comprehensive conservative management including physical therapy, injections, and radiofrequency ablation
• Lateral transfixing technique preferred over posterior non-transfixing approach

Recent evidence indicates minimally invasive SI joint arthrodesis is safe and effective for improving pain, disability, and quality of life at 2-year follow-up compared to conservative management 7, 6.

Critical Pitfalls to Avoid

• Do not perform multiple invasive procedures simultaneously—only one invasive modality should be used at a time to avoid cumulative risks and confounding diagnostic accuracy 8
• Do not proceed to surgery with only single diagnostic block—this reduces diagnostic accuracy and surgical success rates 1
• Do not attribute pain to SI joint without excluding alternative sources (lumbar stenosis, hip pathology, degenerative disc disease) 8, 3
• Distinguish mechanical from inflammatory SI joint pain using imaging patterns: mechanical shows findings restricted to load-bearing zones with vacuum phenomenon and osteophytes, while inflammatory shows diffuse bone marrow edema and erosions 3