Sacroiliac (SI) joint dysfunction is low back pain that comes from the sacroiliac joints. They sit where the base of the spine meets the pelvis, one on each side. They barely move — a few millimeters. They are built to pass the weight of your upper body into your legs, not to give range of motion. When one of them becomes a pain source, it looks exactly like a low back spine problem. But it is not one.
That is the core difficulty with this diagnosis. Low back imaging photographs the low back spine. A joint below the area being looked at cannot be found in a picture that leaves it out. And a patient whose scan shows some ordinary wear gets an explanation that sounds right but happens to be wrong.
According to PubMed, reviews of controlled test blocks put the sacroiliac joint at 10 to 27 percent of suspected chronic low back pain. Using a double-block method, it ran as high as 38 percent, depending on who was studied (Rupert MP, Lee M, Manchikanti L, Datta S, Cohen SP. Evaluation of sacroiliac joint interventions: a systematic appraisal of the literature. Pain Physician. 2009;12(2):399-418. PubMed; and Hansen HC, et al. Pain Physician. 2007;10(1):165-84. PubMed).
About one in five is a large share of a huge group of people. It is also a share that goes unnoticed so often that “nothing showed up on my MRI” is one of the most common first lines we hear. We hear it from patients who turn out to have this.
Three routes account for most of it.
Wear at the joint also builds up with age. And inflammatory disease is its own category. Sacroiliitis in axial spondyloarthritis is a different disease with a different treatment. Sorting mechanical SI joint pain from inflammatory sacroiliitis is part of the evaluation, not an afterthought.
The pattern patients describe is fairly consistent once you know to ask for it:
The conditions it is most often confused with are worth naming, because each has a different answer. They are low back nerve root pain, facet joint pain, piriformis syndrome, cluneal neuropathy, trochanteric pain, and hip joint disease presenting in the groin. Several of these can be present in the same patient at once. That is exactly why guessing does not work.
This diagnosis combines the exam with a test block. It is not made on imaging, and it is not made on a hunch.
Examination. Specific moves stress the joint in specific directions — squeezing, pulling apart, thigh thrust, and related tests. Any one of them is unreliable alone. But several positive together, in a patient whose pain sits below the belt line and to one side, raises enough suspicion to justify the next step. According to PubMed, reviews rate the evidence for these tests alone as limited. That is exactly why they are used to pick who gets a block, not to make the diagnosis.
Imaging, read against symptoms. Wear at the sacroiliac joint is common in people with no pain at all. So a CT or MRI finding does not prove the joint is the source. Imaging earns its place by ruling other things in or out. It also finds inflammatory sacroiliitis when that is the real story.
The diagnostic block, which is the actual test. A small dose of numbing drug is placed into the joint under fluoroscopic guidance. If the pain drops while the drug works and comes back as it wears off, the joint has identified itself. If not, the joint is not the source, and we look elsewhere. That is a useful result, not a failed procedure.
The numbers show why this step cannot be skipped. According to PubMed, a single uncontrolled sacroiliac joint injection gives a false positive about 20 percent up to 54 percent of the time, depending on the study. That is why the diagnosis is held to a controlled or compared block. Two numbing drugs that last different lengths of time are used, and the relief must match the drug (Rupert MP, et al. Pain Physician. 2009. PubMed). One positive injection is evidence. It is not proof. Treating it as proof is how people end up with procedures aimed at the wrong structure.
The SI joint injection page covers what that day involves. In short: local numbing, no sedation, and awake the whole time. Most patients drive themselves home and are back to normal activity, including work, within two to four hours.
Conservative care, aimed at the pelvis rather than the lumbar spine. This matters. A general low back program often misses, because the problem is how load passes through the pelvic ring. Targeted physical therapy builds hip and buttock strength and pelvic control. It also works on the imbalances that made one side carry more. When a walking problem or a leg length difference drives it, dealing with that is treatment, not housekeeping.
Injection, which is both diagnostic and therapeutic. The same image-guided injection that confirms the joint often relieves it too, sometimes for months. How long the relief lasts is itself useful for deciding what to do next.
Radiofrequency ablation of the nerves supplying the joint. When injections give real but short-lived relief, radiofrequency techniques can stretch it out by blocking the joint’s nerve supply, without fusing anything. To be plain: according to PubMed, reviews rate the evidence for sacroiliac radiofrequency treatment as limited. That speaks to the strength of the published research. It does not mean it fails to help patients. It is a reason to discuss expectations honestly, not a reason to hold back the option.
Metabolic and inflammatory drivers. Joint pain does not sit apart from the rest of your body. Inflammation, insulin resistance and body weight all change how well a weight-bearing joint handles load. This practice treats those along with the joint instead of referring them out — see medical weight management and lifestyle medicine.
Fusion, where the joint has been proven and relief will not hold. Minimally invasive SI joint fusion uses the iFuse and Catamaran implant systems. It steadies the joint so bone can grow across it. That page has the randomized trial evidence, the implant comparison, the sedation and recovery plan, and the coverage position in full.
Fusion is surgery, and this practice performs it. Dr. Gurpreet Singh Padda, MD, MBA, MHP is a licensed physician and surgeon with surgical privileges.
It is the right answer when three things are all true. A test block has confirmed the joint as the pain source. Conservative (non-surgical) care has truly been tried, not just offered. And the relief from injection or ablation is real but does not last. Every major trial of SI joint fusion required block confirmation before enrolling a patient. Coverage rules usually require it too. This is one case where what an insurer asks for and what good practice asks for point the same way.
It is the wrong answer in the cases behind most of the letdowns with this procedure. A fusion on a joint never proven to be the pain source has no reason to work. Neither does one on a patient whose main problem is a low back nerve root, or a hip. Nor one on inflammatory sacroiliitis that needs a rheumatologist and a disease-changing drug, not an implant. And a patient with several pain sources may get a real partial result from fusing one. That is a fair goal, but only if it was the expectation going in.
So the order is: prove the joint, treat with conservative (non-surgical) care and procedures, and save fusion for the patients who have finished that order, not skipped it.
Does your pain sit low and to one side? Did it start after a fusion or a pregnancy? Has your low back workup never explained it? Then the sacroiliac joint is worth testing directly. We see patients from across St. Louis, Florissant, St. Charles and the Illinois Metro East. Call us or request an evaluation.
Sometimes numbing blocks confirm the sacroiliac joint is the pain source, and cortisone keeps wearing off. Then an image-guided intra-articular injection with your own platelets or marrow cells treats the worn joint lining and ligaments. It does not just silence them for a few more months. PRP injections and bone marrow concentrate are both options. See how the choice is made on our orthobiologic treatment page.
Because a low back MRI images the low back spine. Even when the sacroiliac joints are included, wear there is common in people with no pain at all. This diagnosis is not made on a picture. It combines exam findings with an image-guided numbing block. The block either stops your pain for a while or it does not. Read more: Diagnosing sacroiliac joint pain with an injection.
Sciatica follows a nerve root. It usually travels below the knee and often brings numbness, tingling or weakness along a set path. Coughing or sneezing often sets it off. SI joint pain is usually pointed to with one finger just inside the back of the pelvis. It spreads into the buttock and back of the thigh. Standing on one leg sets it off, not nerve stretch. Both can exist in the same patient. That is why testing beats assuming. Read more: Sciatica: disc, piriformis or cluneal nerve?
It is one of the likeliest causes, and one of the most often missed. Fusing segments above the pelvis shifts load downward, and the joint below the fusion takes it. New, low, one-sided pain after an operation that otherwise went well deserves a direct look at the sacroiliac joint. Do not settle for another round of low back imaging. Read more: Why leg pain persists after back surgery.
No. The injection is done under local numbing with the patient awake and able to respond. Most patients drive themselves home and are back to normal activity, including work, within two to four hours. SI joint fusion is a different procedure with a different plan. It uses mild sedation, a driver is required, and there is a lifting limit afterward. All of that is explained before anything is booked. Read more: Diagnosing sacroiliac joint pain with an injection.
No — it answered the question it was asked. Short relief that matches the numbing drug and the steroid confirms the joint is the source. That decides everything that follows. Relief that lasts is a treatment. Relief that fades is a diagnosis. Both are useful. The second often makes a patient a candidate for something longer lasting. Read more: Why pain injections stop working.
No, and mixing them up delays real treatment. Inflammatory sacroiliitis in axial spondyloarthritis is an immune disease. It improves with exercise, is worse after rest, and wakes people in the second half of the night. It is treated with anti-inflammatory and disease-changing medicine. Mechanical SI joint pain is worse with load and better with rest. The histories differ. Tell us which one yours sounds like. Read more: When autoimmunity is the source of pain.
For many patients it does a lot, as long as it targets the pelvis and hips, not a general low back program. Buttock and hip strength, pelvic control, and fixing uneven loading treat the cause, not just the symptom. It is the right place to start. And it stays useful once an injection is in the plan. Read more: Hip-focused physical therapy for low back pain.
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