SI Joint Pain: Where It Hurts, What Causes It and How It Is Treated

Medically reviewed by Dr. Edward Baumgartner Jr., MD on Nov 4, 2026

The sacroiliac (SI) joints sit where the base of your spine meets your pelvis, one on each side. When one of them is the source of pain, the ache is usually low in the back and off to one side. It's easy to mistake for a disc problem, sciatica or a sore hip. A 2025 multispecialty guideline estimates that the SI joint complex causes pain in 15% to 30% of people whose back pain sits mostly below the lowest lumbar vertebra [3].

What is SI joint pain?

Quick answer: SI joint pain is pain from one of the two joints where the base of the spine meets the pelvis. It usually sits low in the back and off to one side, and it can spread into the buttock, outer hip, groin or leg. It is easy to mistake for a disc problem, sciatica or a sore hip. [1][3]

What the SI joint does

Each SI joint links the sacrum, the triangle-shaped bone at the bottom of the spine, to the ilium, the large wing of the pelvis. The joint absorbs shock and passes the weight of the upper body from the spine down into the legs [1]. Pain can start inside the joint or in the ligaments around it [3].

Common SI joint pain symptoms

Quick answer: Common SI joint pain symptoms are pain low in the back on one side, at or just below the bony bump at the back of the pelvis. The pain can spread into the buttock, outer hip, groin or leg. It often flares with stairs, long car rides, standing for a long time or turning over in bed. [1]

Many people with SI joint pain can point to it with one finger, at or just below and inside the bony bump at the back of the pelvis. Doctors call this the Fortin finger test [1]. Other common features [1]:

• Pain on one side, sometimes both, but usually not in the middle of the spine
• Pain that spreads into the buttock, the outer hip, the groin or the leg
• Pain that flares with stairs, long car rides, standing for a long time, turning over in bed, lying on the sore side or shifting weight onto that leg

Women are more likely than men to have SI joint pain, and it is common during pregnancy and after childbirth [1].

What can cause SI joint pain

Quick answer: The exact cause of SI joint pain is often not clear. Things linked to it include arthritis in the joint, such as osteoarthritis or ankylosing spondylitis, an injury like a fall onto the buttocks, sports with repeated pounding or twisting, and pregnancy and the months after delivery. [1]

The exact cause is often not clear [1]. Things linked to SI joint pain include [1]:

• Arthritis in the joint, including osteoarthritis and inflammatory types such as ankylosing spondylitis
• An injury, such as a fall onto the buttocks, heavy lifting or a car accident
• Sports with repeated pounding or twisting, such as football, gymnastics and golf
• Pregnancy and the months after delivery

SI joint pain vs sciatica: how to tell them apart

Quick answer: SI joint pain can spread into the leg, so it can feel like sciatica. Numbness, tingling, leg weakness or pain that shoots down the leg point more toward a nerve problem such as a herniated disc. Facet joint pain, piriformis syndrome and hip problems can also cause pain in the same area. [1]

Several conditions cause pain in the same area and need to be ruled out [1]. Our back pain page covers other common causes.

• Herniated lumbar disc. More likely to bring numbness or tingling in the legs or feet, leg weakness, or pain that shoots down the leg [1]. This nerve pain is what most people mean by sciatica. Our sciatica page covers it in more detail.
• Facet joint pain. Often worse when you lean backward [1].
• Piriformis syndrome. Trouble sitting, with pain running down the back of one or both legs [1].
• Hip problems. Pain with activity or long sitting, sometimes with locking or clicking in the joint [1]. See hip pain.

How SI joint pain is diagnosed

Quick answer: No single test settles it. A doctor starts with your history and an exam, then uses a set of provocation tests. MRI, CT and bone scans do not reliably show the SI joint as the pain source, but they help rule out other causes. A numbing block placed with X-ray guidance can support the diagnosis. [1][3]

No single test settles it. A doctor usually starts with your history, an exam of the spine, pelvis and hips, and a check of the nerves in your legs [1].

Provocation tests. The doctor presses on or moves your pelvis in five standard ways to see whether your usual pain comes back. One test on its own isn't reliable. In a 2005 study, three or more positive tests out of five pointed to the SI joint with reasonable accuracy [4]. The 2025 guideline adds that a negative set of tests does more to rule the joint out than a positive set does to rule it in [3].

Imaging. MRI, CT and bone scans do not reliably show whether the SI joint is the pain source [1][3]. They still help rule out other causes, such as a fracture, an infection or a tumor [1].

A diagnostic block. Using X-ray guidance, the doctor places numbing medicine in the joint. If your usual pain drops while the medicine is working, that supports the SI joint as the source [1][3]. Before radiofrequency ablation, the block is usually aimed at the small nerves behind the joint instead [2][3].

Treatment options, from first steps to procedures

Quick answer: Treatment usually starts with the least invasive option. Physical therapy, exercise and anti-inflammatory medicine come first. If pain lasts beyond about 4 weeks of conservative care, an image-guided steroid injection may be next. Radiofrequency ablation is considered after a nerve block gives meaningful relief, and fusion is limited to carefully selected patients. Results vary. [1][2][3]

Treatment usually starts with the least invasive option. The American Society of Pain and Neuroscience (ASPN) guideline says conservative care should come first, and it notes that most acute SI joint pain settles with it [2].

Exercise, physical therapy and medicine

Physical therapy that strengthens and stretches the muscles around the pelvis and hips is a first-line option. It is sometimes combined with hands-on joint manipulation [1]. Anti-inflammatory medicine may help as part of the plan [1]. During pregnancy or after delivery, a pelvic belt may also help [1].

Image-guided injections

If pain lasts beyond about 4 weeks of conservative care, the ASPN guideline recommends an image-guided steroid injection into the joint [2]. Studies report at least 4 weeks of relief in well-selected patients, both from steroid injected into the joint and from steroid injected around it [3]. Results vary. How much the injection helps also guides what comes next. Learn more about injections and nerve blocks.

Radiofrequency ablation

Radiofrequency ablation uses heat to quiet the small nerves that carry pain signals from the back of the joint. It is considered after a diagnostic nerve block gives meaningful relief [2][3]. The 2025 guideline rated the evidence as strong that this can provide relief for at least 6 months when the pain comes from the structures around the joint [3]. In a small placebo-controlled trial of 28 people, 8 of the 14 treated patients still had at least 50% pain relief and better function at 6 months. By one year, 2 of the 14 still had relief [5]. Results vary. See radiofrequency ablation.

SI joint fusion

Fusion is for people with confirmed SI joint pain that has not improved with conservative care and less invasive procedures [1]. Through a small incision, an implant or bone graft is placed across the joint to stabilize it [8]. Two randomized trials compared fusion using triangular titanium implants with nonsurgical care. Studies report larger improvements in pain and function at 1 and 2 years in the fusion groups [6][7]. Results vary, and those trials tested one implant design. Surgery has risks, and in one trial adverse events were slightly more common after fusion [6]. The 2025 guideline rated the evidence for benefit lasting at least one year as weak or very weak, and it limits fusion to carefully selected patients [3]. Read more about SI joint fusion in Houston.

When to get checked sooner

Don't wait to be seen if back or pelvic pain comes with a recent fall or injury, fever, weight loss you can't explain, changes in bladder or bowel control, a history of cancer, or pain at night. Doctors check for these signs to rule out a more serious cause [1]. More in when back pain needs a specialist.

SI joint pain care at HTx Pain Institute

HTx Pain Institute sees patients at our Willowbrook office and our Humble office. Our services for SI joint pain include image-guided injections and nerve blocks and SI joint fusion. Dr. Edward Baumgartner Jr., MD, reviews your history, exam and imaging and walks you through the options that fit your diagnosis. Call (832) 960-7160 or request an appointment.

Common questions

Where is SI joint pain felt? Usually low in the back on one side, at or just below the bony bump at the back of the pelvis. It can spread into the buttock, outer hip, groin or leg [1].

Can SI joint pain feel like sciatica? It can, because SI joint pain may spread into the leg [1]. Numbness, tingling or leg weakness point more toward a nerve problem such as a herniated disc [1].

Will an MRI show SI joint pain? Not reliably. Imaging can't confirm the SI joint as the pain source, but it can rule out other causes [1][3].

Does SI joint pain go away on its own? The ASPN guideline notes that most acute SI joint pain settles with conservative care such as activity changes and physical therapy [2].

Is surgery the only long-term option? No. Care usually starts with exercise and physical therapy, and injections and radiofrequency ablation come before surgery [1][2]. Fusion is reserved for carefully selected patients [1][3].

This article is for general information and is not medical advice. Talk with your doctor about your own situation.

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