Sacroiliac Joint Dysfunction
Sacroiliac (SI) joint dysfunction occurs when the joint connecting the sacrum (base of the spine) to the pelvis becomes inflamed, hypermobile, or stiff, causing lower back and buttock pain. The SI joint transmits all forces between the upper body and legs; when its mechanics are disrupted, the surrounding ligaments, muscles, and joint surfaces become irritated. It is estimated to account for 15-25% of all low back pain and is frequently misdiagnosed as a lumbar disc or nerve problem.
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Symptoms
- Low back pain at or just below the belt line, often one-sided
- Buttock pain, often mistaken for sciatica
- Pain that radiates down the back of the thigh, rarely below the knee
- Pain worsening with standing, walking, climbing stairs, or transitioning from sitting to standing
- Relief when lying down or sitting still
- Tenderness directly over the SI joint when pressed
When to See a Doctor
Seek evaluation if lower back or buttock pain persists beyond 6 weeks and has not responded to standard back treatments. SI joint dysfunction is a clinical diagnosis confirmed with specific provocation tests (FABER, FADIR, posterior shear). A diagnostic SI joint injection that temporarily eliminates 75-80% of pain is considered the gold standard for confirmation.
Treatment Options
Physical therapy and stabilization exercises
Core strengthening, pelvic stabilization, and manual therapy address underlying joint instability or stiffness. First-line treatment for most patients.
SI joint injection
Fluoroscopy- or CT-guided injection of cortisone into the SI joint provides pain relief and serves as both treatment and diagnostic confirmation. Effects last weeks to months.
Radiofrequency ablation
Uses heat to interrupt the nerves transmitting SI joint pain signals. Provides longer-lasting relief (1-2 years) than injection for appropriately selected patients.
SI joint fusion
Minimally invasive surgery placing titanium implants across the SI joint to fuse and stabilize it permanently. Reserved for patients who fail all conservative measures and have confirmed SI joint as the pain source.
Recovery Timeline
Physical therapy: 6-12 weeks for meaningful improvement. Injections: relief within days to weeks, lasting 2-6 months. Radiofrequency ablation: 1-2 years. SI joint fusion: return to most activities by 3-6 months, full recovery by 12 months.
Frequently Asked Questions
How is SI joint dysfunction different from a herniated disc?
Both cause lower back pain but in different patterns. Disc pain typically radiates down the leg in a specific nerve distribution and is often associated with numbness or weakness. SI joint pain is usually localized to the buttock and posterior thigh and rarely extends below the knee. Physical examination tests that stress the SI joint reproduce the pain. Imaging alone often cannot distinguish them; the diagnostic injection is the definitive test.
Can pregnancy cause SI joint dysfunction?
Yes. The hormone relaxin released during pregnancy loosens all pelvic ligaments, including those stabilizing the SI joint. Combined with the postural shift from a growing belly, this frequently causes SI joint pain during and after pregnancy. Postpartum SI joint pain is very common and usually responds well to physical therapy and a pelvic stabilizing belt. In persistent cases, injection and rarely surgery are options.
Is SI joint fusion a major surgery?
By spine surgery standards, no. The procedure takes about an hour through a small lateral incision; three titanium implants are placed across the joint under fluoroscopic guidance. Recovery is faster than open lumbar fusion, with most patients walking the same day and back at a desk within 1-2 weeks. Patient selection, confirming the SI joint is truly the pain source, is what determines outcomes more than anything else.
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This information is for educational purposes only and is not a substitute for professional medical advice. Always consult a qualified healthcare provider for diagnosis and treatment.