Medically reviewed by Keley John Booth, MD, D.ABA · Board-certified, interventional pain management · Updated May 2026
What your SI joint is — and why it flares
Your sacroiliac (SI) joints sit where the base of your spine (the sacrum) meets your pelvis — one on each side, just below the dimples in your lower back. They're small but strong joints that absorb shock and pass load between your upper body and your legs. When an SI joint moves too much, too little, or gets inflamed (swollen), it can cause a deep, nagging pain low in your back and buttock — sometimes spreading into the hip or the back of the thigh, but usually stopping above the knee.
SI joint pain is often mistaken for a disc problem or sciatica. The real question is what's stressing the joint. Common causes we see at our Oklahoma clinics:
- Pregnancy and childbirth — ligaments loosen and the pelvis shifts, leaving the joint less stable
- A fall or injury — a sudden impact, like landing hard on one side
- Arthritis — wear-and-tear or inflammatory arthritis affecting the joint
- A previous lower-back fusion — nearby fused vertebrae push extra load onto the SI joint
- Uneven leg length or an altered walking pattern — small imbalances add up over time
- Repetitive stress — heavy lifting, or sports with a lot of twisting and impact
Important: SI joint pain is one of the most commonly missed causes of lower back pain. It's often treated as a disc problem for months before the real source is found. Pinpointing it correctly is the whole game.
Warning signs you shouldn't ignore
Get evaluated urgently if you have:
- Loss of bladder or bowel control
- Numbness in the groin, saddle area, or inner thighs
- Sudden or worsening weakness in a leg
- Pain right after a fall, crash, or other trauma
- Fever, unexplained weight loss, or night sweats along with the pain
- A history of cancer with new, constant back pain
These signs are uncommon, but they matter. Most SI joint pain is treatable without surgery — the rare case that signals something more serious needs attention quickly.
How we approach SI joint pain
We work from the least invasive option to the most, and we don't move forward until we're confident the SI joint is the real source.
Targeted Diagnosis
A focused exam with hands-on movement tests that stress the SI joint, plus a careful history. We rule the disc and nerve causes in or out instead of guessing.
Confirm the Source
An image-guided numbing injection into the joint. If your pain drops sharply, we've confirmed the SI joint is the problem — and we know exactly what to treat.
Conservative Care
Targeted physical therapy for pelvic and core stability, activity changes, anti-inflammatory (anti-swelling) medication, and a support belt when it helps.
Image-Guided Injections & Nerve Treatment
Therapeutic steroid injections to calm the joint, and radiofrequency ablation of the small nerves around it for longer-lasting relief.
Advanced & Surgical Options — When Truly Indicated
Regenerative options for select patients, and a referral for minimally invasive SI joint fusion only in the rare case that hasn't responded to everything else.
Treatments we use for SI joint pain
- Image-Guided SI Joint Injections — both pinpoint the source and calm the joint
- Radiofrequency Ablation — quiets the small nerves around the joint for lasting relief
- Facet Joint Injections — when nearby spine joints share the blame
- Regenerative Therapies — biologic options for select patients
- Coordinated Physical Therapy — pelvic and core stability to protect the joint
Frequently asked questions
How do I know the pain is from my SI joint and not a disc?
SI joint pain usually sits low and to one side — in the back or the buttock — and flares when you stand up, climb stairs, or roll over in bed. A disc problem or sciatica more often shoots down the leg past the knee. The surest way to tell is a simple image-guided numbing injection: if your pain drops, we've found the source.
Will SI joint pain go away on its own?
Mild cases can settle with activity changes and time. But pain that lingers past a few weeks, or keeps coming back, usually has a mechanical cause that won't fix itself. A focused evaluation saves you months of guessing.
Do I need surgery for SI joint pain?
Almost never to start. The large majority of people improve with therapy, injections, and nerve treatments. Minimally invasive SI joint fusion exists for the rare case that doesn't respond — and we'll only refer you for it if it's truly the right call.
Can SI joint pain come from a past back surgery?
Yes. After a lower-back fusion, the SI joint carries extra load and can become a new source of pain. If your back pain changed or moved lower after surgery, the SI joint is worth checking.
What does an SI joint injection feel like?
It's a quick, image-guided outpatient procedure. We numb the skin first, then place medication into or around the joint using live X-ray for accuracy. Most people are back to normal activity the next day.