The sacroiliac joints sit where the base of the spine meets the pelvis, one on each side. They barely move — a few millimeters — because they are built to transfer the load of your upper body into your legs rather than to provide range of motion. When one of them becomes a pain generator, it produces a complaint that looks exactly like a lumbar spine problem and is not one.
That is the central difficulty with this diagnosis. Lumbar imaging photographs the lumbar spine. A joint that sits below the field of interest cannot be found in a picture that does not include it, and a patient whose scan shows some ordinary degenerative change gets a plausible-sounding explanation that happens to be the wrong one.
According to PubMed, systematic reviews of controlled diagnostic blocks put the sacroiliac joint at between 10 and 27 percent of suspected chronic low back pain, and as high as 38 percent under a double-block paradigm depending on the population 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).
Roughly one in five is a large share of an enormous population. It is also a share that goes unrecognized often enough that “nothing showed up on my MRI” is one of the more common opening sentences we hear from patients who turn out to have this.
Three routes account for most of it.
Degenerative change at the joint also accumulates with age, and inflammatory disease is its own category: sacroiliitis in axial spondyloarthritis is a different disease with a different treatment, and separating mechanical SI joint pain from inflammatory sacroiliitis is part of the evaluation rather than an afterthought.
The pattern patients describe is reasonably 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: lumbar radiculopathy, 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 the same time, which is precisely why guessing does not work.
This is a diagnosis made by combining examination with a diagnostic block. It is not made on imaging, and it is not made on a hunch.
Examination. Provocative maneuvers stress the joint in specific directions — compression, distraction, thigh thrust, and related tests. Any single one of them is unreliable on its own. Several positive together, in a patient whose pain sits below the belt line and to one side, raises suspicion enough to justify the confirmatory step. According to PubMed, the systematic reviews rate the evidence for provocative testing alone as limited, which is exactly why it is used to select who gets a block rather than to make the diagnosis.
Imaging, read against symptoms. Degenerative change at the sacroiliac joint is common in people with no pain at all, so a CT or MRI finding does not establish the joint as the source. Imaging earns its place by ruling other things in or out, and by identifying inflammatory sacroiliitis where that is the real story.
The diagnostic block, which is the actual test. A small volume of local anesthetic is placed into the joint under fluoroscopic guidance. If the pain falls reliably while the anesthetic is working and returns as it wears off, the joint has identified itself. If it does not, the joint is not the source and we go looking elsewhere — which is a useful result, not a failed procedure.
The reason this step is non-negotiable is in the numbers. According to PubMed, the false-positive rate of a single uncontrolled sacroiliac joint injection runs from roughly 20 percent up to 54 percent depending on the series, which is why a controlled or comparative block — two anesthetics of different duration, with the relief tracking the drug — is the standard the diagnosis is held to (Rupert MP, et al. Pain Physician. 2009. PubMed). One positive injection is evidence. It is not proof, and 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 anesthetic, no sedation, awake throughout, most patients drive themselves home and resume normal activity, including work, within two to four hours.
Conservative care, aimed at the pelvis rather than the lumbar spine. This distinction matters. A generic low back program frequently misses, because the problem is load transfer through the pelvic ring. Targeted physical therapy works on hip and gluteal strength, pelvic control, and the asymmetries that made one side carry more than the other. Where a gait abnormality or leg length difference is driving it, addressing that is treatment rather than housekeeping.
Injection, which is both diagnostic and therapeutic. The same image-guided injection that confirms the joint also frequently relieves it, sometimes for months. How long the relief holds is itself diagnostic information about what to do next.
Radiofrequency ablation of the nerves supplying the joint. Where injections give real but temporary relief, radiofrequency techniques can extend it by interrupting the nerve supply, without fusing anything. Worth knowing plainly: according to PubMed, the systematic reviews rate the evidence for sacroiliac radiofrequency neurotomy as limited. That is a statement about the strength of the published literature, not a statement that it does not help patients — and it is a reason to discuss expectations honestly rather than a reason to withhold the option.
Metabolic and inflammatory drivers. Joint pain does not sit apart from the rest of your physiology. Inflammatory load, insulin resistance and body weight all change how a load-bearing joint tolerates being loaded. This practice treats those alongside the joint rather than 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 using the iFuse and Catamaran implant systems stabilizes the joint so bone can grow across it. That page carries the randomized-trial evidence, the implant comparison, the sedation and recovery protocol, and the coverage position in full.
Fusion is a surgical procedure 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 conditions are all met: the joint has been confirmed as the pain source by diagnostic block, conservative care has genuinely been tried rather than nominally offered, and the relief from injection or ablation is real but does not hold. Every major trial of SI joint fusion required block confirmation before enrolling a patient, and coverage policy generally requires it too. This is one of the cases where what a payer asks for and what good practice asks for point the same direction.
It is the wrong answer in the situations that produce most of the disappointment with this procedure. A fusion performed on a joint that was never proven to be the pain generator has no reason to work. Neither does one performed on a patient whose dominant problem is a lumbar nerve root, or a hip, or inflammatory sacroiliitis that needs a rheumatologist and a disease-modifying drug rather than an implant. And a patient with several pain generators at once may get a genuine partial result from fusing one of them — which is a reasonable outcome to aim for, but only if it was the expectation going in.
The sequence, therefore: prove the joint, treat conservatively and interventionally, and reserve fusion for the patients in whom that sequence has been completed rather than skipped.
If your pain sits low and to one side, if it started after a fusion or a pregnancy, or if your lumbar workup has never explained it, the sacroiliac joint is worth testing directly. We see patients from across St. Louis, Florissant, St. Charles and the Illinois Metro East. Call (314) 481-5000 or request an evaluation.
Because a lumbar MRI images the lumbar spine, and even when the sacroiliac joints are included, degenerative change there is common in people with no pain at all. This diagnosis is not made on a picture. It is made by combining examination findings with an image-guided anesthetic block that either abolishes your pain temporarily or does not. Read more: Diagnosing sacroiliac joint pain with an injection.
Sciatica follows a nerve root — it usually travels below the knee, often carries numbness, tingling or weakness in a specific distribution, and is frequently provoked by coughing or sneezing. SI joint pain is usually pointed to with one finger just inside the back of the pelvis, refers into the buttock and back of the thigh, and is provoked by single-leg loading rather than by nerve tension. Both can exist in the same patient, which is why testing beats assuming. Read more: Sciatica: disc, piriformis or cluneal nerve?
It is one of the likeliest explanations and one of the most frequently missed. Fusing segments above the pelvis transfers load downward, and the joint below the construct takes it. Pain that is new, low and one-sided after an operation that otherwise went well deserves a direct look at the sacroiliac joint rather than another round of lumbar imaging. Read more: Why leg pain persists after back surgery.
No. The injection is performed under local anesthetic with the patient awake and responsive, and most patients drive themselves home and resume normal activity, including work, within two to four hours. SI joint fusion is a different procedure with a different protocol — it uses mild sedation, a driver is required, and there is a lifting restriction afterwards, all of which is explained before anything is scheduled. Read more: Diagnosing sacroiliac joint pain with an injection.
No — it answered the question it was asked. Temporary relief that tracks the anesthetic and the steroid confirms the joint is the source, which is what determines everything that follows. Relief that holds is a treatment; relief that fades is a diagnosis. Both are useful, and the second one is often what makes a patient a candidate for something more durable. Read more: Why pain injections stop working.
No, and confusing them delays real treatment. Inflammatory sacroiliitis in axial spondyloarthritis is an immune-driven disease that improves with exercise, is worse after rest, wakes people in the second half of the night, and is treated with anti-inflammatory and disease-modifying medication. Mechanical SI joint dysfunction is worse with loading and better with rest. The histories are different, and it is worth telling us which one yours sounds like. Read more: When autoimmunity is the source of pain.
For many patients it does a great deal, provided it is aimed at the pelvis and hips rather than at a generic low back protocol. Gluteal and hip strength, pelvic control, and correcting asymmetric loading address the mechanism rather than the symptom. It is the appropriate place to start, and it does not stop being useful once an injection is in the plan. Read more: Hip-focused physical therapy for low back pain.
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