Could It Be SI Joint Imbalance?
Yes, sacroiliac (SI) joint dysfunction is a highly plausible cause of chronic low back pain, accounting for 15-30% of chronic mechanical low back pain cases. 1, 2, 3
Diagnostic Approach
Clinical Presentation to Look For
The SI joint should be suspected when pain is:
- Localized to the gluteal region with possible radiation to the lower lumbar region, groin, or lower limbs 3
- Unilateral or asymmetric in distribution 1
- Worsened by transitional movements (sitting to standing, climbing stairs) 1
Critical point: Neither history nor physical examination alone can reliably diagnose SI joint pain—you need a systematic approach combining multiple elements. 4
Physical Examination Strategy
Perform a battery of at least 3-5 provocative tests—individual tests have weak predictive value, but when three or more tests are positive, the specificity and sensitivity become clinically useful. 1, 2 Common provocative maneuvers include:
- FABER (Patrick's test)
- Gaenslen's test
- Thigh thrust test
- Compression test
- Distraction test 1
Pitfall to avoid: Do not rely on a single positive provocative test—this has poor diagnostic accuracy. 2, 3
Imaging Recommendations
Start with plain radiographs of the pelvis/SI joints to exclude red flags (fractures, tumors, infection) and assess for degenerative changes, sclerosis, and joint space narrowing. 4, 5
Do NOT routinely order MRI unless you suspect inflammatory sacroiliitis/axial spondyloarthropathy, which typically presents in younger patients (20s-40s) with inflammatory back pain that improves with exercise and worsens with rest. 4, 5
Key distinction:
- Mechanical SI joint dysfunction (degenerative): Plain radiographs sufficient 5
- Inflammatory sacroiliitis (axSpA): Requires MRI with fluid-sensitive sequences (STIR or T2-weighted fat-suppressed) to detect bone marrow edema before radiographic changes appear 4, 6
Important caveat: Anatomic landmark-guided SI joint injections have a 78-100% miss rate—always use image guidance (fluoroscopy preferred, ultrasound acceptable). 4
Diagnostic Confirmation
The gold standard for diagnosis is an image-guided intra-articular SI joint injection with local anesthetic, looking for ≥75% acute pain relief. 4, 1, 7
Critical limitation: False-positive rates range from 11-63%, so interpret results cautiously. 4 Some experts recommend dual blocks to improve specificity, though this is not standard practice. 4
Treatment Algorithm
First-Line (Conservative Management)
Implement a multimodal program combining:
- Patient education on posture and movement patterns 1, 3
- Pelvic girdle stabilization exercises with focused stretching performed by physical therapists or clinicians trained in manipulative therapy 1
- Manual manipulation therapy 1, 3
- Pelvic belts (particularly beneficial in postpartum patients) 1
- NSAIDs and acetaminophen for analgesia 5
Second-Line (Interventional)
If conservative treatment fails after 6-12 weeks:
Intra-articular corticosteroid injections have the highest evidence rating (1 B+) and can produce pain relief for >3 months in some patients. 4, 2, 3
Third-Line (Advanced Interventional)
If corticosteroid injections provide only short-term relief:
Cooled radiofrequency ablation (RFA) of the L5 dorsal ramus and S1-3 (or S4) lateral branches demonstrates the strongest evidence for efficacy. 4, 2, 3 This has a low complication rate and should be considered before surgical options. 2
Fourth-Line (Surgical)
Minimally invasive SI joint fusion may be considered in appropriately selected patients who fail all conservative and interventional treatments, with increasingly favorable outcomes reported in the literature. 7
Clinical Pearls
- SI joint dysfunction accounts for 10-38% of low back pain cases—it is common and frequently overlooked. 8
- Always examine adjacent structures (hip and lumbar spine) as these can refer pain to the SI region. 8
- Lumbar fusion surgery predisposes patients to more rapid SI joint degeneration. 8
- The reported complication rate for SI joint treatments is low across all modalities. 2