If you have been living with persistent lower back pain and were told it is a herniated disc, there is a reasonable chance that diagnosis is either incomplete or outright wrong. Research shows that sacroiliac joint dysfunction accounts for 15 to 30 percent of all chronic low back pain cases, and a striking 72.3 percent of patients with confirmed lumbar disc herniation also have co-existing SI joint dysfunction. The overlap between these two conditions is so significant that even experienced clinicians routinely confuse them, and patients often spend years chasing the wrong treatment. Consider the patient who undergoes lumbar disc surgery only to wake up with the same pain — in patients with failed back surgery syndrome, SI joint dysfunction turns out to be the actual pain source in up to 40 to 63 percent of cases, according to data published in NCBI StatPearls. The eight symptoms outlined in this article are ones that belong to SI joint dysfunction but are commonly blamed on a herniated disc.
Some of them, like one-sided lower back pain and leg numbness, overlap so heavily that imaging alone cannot sort them out. Others, like groin pain and pelvic instability, are distinct enough to serve as red flags if your doctor knows to look for them. For most of the 20th century, the SI joint was largely ignored as a pain source, which means historical misdiagnosis has been extremely common — and the pattern still persists today. This article walks through each of the eight mistaken symptoms, explains why the confusion happens, covers the diagnostic tests that can actually tell these conditions apart, and discusses what it means for treatment when both problems exist at the same time. If you or someone you care for has been dealing with chronic back pain that has not responded to disc-focused treatment, what follows may change how you think about the problem entirely.
Table of Contents
- Why Do SI Joint Dysfunction Symptoms Get Mistaken for Herniated Disc Pain?
- Pseudo-Sciatica and Referred Leg Pain — The Most Deceptive Overlap
- Groin and Hip Pain — The Symptoms That Get Blamed on Everything Else
- How Physical Examination Tests Can Distinguish SI Joint Dysfunction from Disc Herniation
- Pelvic Instability and Sleep Disruption — The Overlooked Red Flags
- When Both Conditions Exist at the Same Time
- Moving Toward Better Diagnostic Awareness
- Conclusion
- Frequently Asked Questions
Why Do SI Joint Dysfunction Symptoms Get Mistaken for Herniated Disc Pain?
The fundamental problem is anatomical real estate. The sacroiliac joint sits at the base of the spine where the sacrum meets the pelvis, and it shares nerve supply and referral patterns with the lumbar discs directly above it. When something goes wrong in either structure, the brain receives pain signals from the same general neighborhood. A patient walks into a clinic saying “my lower back hurts on the right side and the pain shoots into my buttock.” That description fits both conditions almost perfectly. The clinician orders an MRI, sees a bulging disc — which is present in a large percentage of adults who have no pain at all — and the diagnosis is made. The SI joint is never examined. A separate study published in PubMed found SI joint dysfunction present in 33.3 percent of patients who had lumbar disc herniation, reinforcing that these conditions frequently coexist rather than occurring in isolation.
This is where diagnosis gets particularly treacherous. It is not always a matter of one or the other. A patient can genuinely have a herniated disc on imaging and still have most of their pain generated by the SI joint. If the treating physician focuses exclusively on the disc, the patient improves only partially — or not at all — and everyone is left wondering why. The American Academy of Family Physicians noted in its 2022 review that SI joint dysfunction remains underdiagnosed precisely because its symptoms mimic lumbar disc disease so convincingly. What makes this especially relevant for older adults and those with neurodegenerative conditions is that chronic unresolved pain is not just a comfort issue. Persistent pain disrupts sleep, reduces mobility, accelerates cognitive decline, and contributes to depression and social isolation — all factors that compound the challenges of dementia care. Getting the right diagnosis matters far beyond the back itself.
Pseudo-Sciatica and Referred Leg Pain — The Most Deceptive Overlap
The single most confusing symptom is pain that radiates from the lower back into the buttock and down the back of the thigh. True sciatica, caused by a herniated disc compressing a nerve root, follows this exact path. But SI joint dysfunction produces what clinicians call “pseudo-sciatica” — hot, sharp, stabbing pain in the buttock and posterior thigh that can be virtually indistinguishable from the real thing. The critical difference, however, is that SI joint referred pain typically does not extend below the knee. True discogenic sciatica frequently travels all the way to the foot, sometimes with specific dermatomal patterns depending on which nerve root is compressed. However, this rule is not absolute, and that is the limitation worth understanding.
Some patients with SI joint dysfunction do report pain that reaches the calf or ankle, particularly when inflammation is severe or when the joint irritation secondarily affects nearby neural structures. In these cases, even the “below the knee” guideline fails as a differentiator, and clinicians must rely on physical examination tests and diagnostic injections to sort things out. The straight leg raise test offers some help here — it is typically positive when a herniated disc is irritating a nerve root but negative when the SI joint is the primary culprit. If your doctor has never performed this test or the cluster of SI joint provocation maneuvers, there is a gap in the workup. Numbness and tingling in the leg further muddies the picture. While these are classically nerve root symptoms associated with disc herniation, Weill Cornell Neurosurgery notes that SI joint dysfunction can also produce numbness, tingling, and even weakness in the leg. For caregivers monitoring an older adult with dementia who cannot reliably describe their symptoms, this overlap makes it even more important to work with a provider who considers both diagnoses simultaneously rather than defaulting to the first MRI finding.
Groin and Hip Pain — The Symptoms That Get Blamed on Everything Else
Groin pain is one of the most underappreciated symptoms of SI joint dysfunction, and it is the one most likely to send patients down the wrong diagnostic path entirely. Published research shows that 46.5 percent of SI joint dysfunction patients report groin pain. Rather than pointing clinicians toward the SI joint, this symptom typically triggers evaluation for hip osteoarthritis, labral tears, inguinal hernias, or upper lumbar disc herniations. A patient can easily end up with a hip replacement referral or abdominal imaging when the real problem is the joint between their sacrum and pelvis. Hip and pelvis pain follows a similar pattern of misdirection.
The Mayfield Clinic and Cedars-Sinai both list pain spreading to the hips and pelvis as a primary symptom of SI joint dysfunction, yet this presentation is routinely attributed to hip bursitis, piriformis syndrome, or referred pain from lumbar disc disease. For example, a 70-year-old woman who reports deep buttock pain and lateral hip aching after walking is far more likely to receive a trochanteric bursitis diagnosis and a cortisone injection into the hip bursa than a thorough SI joint examination. If the injection does not help — and it will not, if the SI joint is the source — the cycle of misdiagnosis continues. The practical takeaway is this: if you or a loved one has pain in the groin, lateral hip, or deep pelvis that has not responded to hip-focused treatment, the SI joint should be formally evaluated. This is especially true in older adults with osteoporosis or degenerative joint changes, where SI joint dysfunction becomes increasingly common but is overshadowed by the more familiar diagnoses that show up on standard imaging.
How Physical Examination Tests Can Distinguish SI Joint Dysfunction from Disc Herniation
The most actionable step for anyone caught in this diagnostic gray zone is to ensure that SI joint provocation testing has actually been performed during a clinical visit. Research demonstrates that a cluster of three or more positive SI joint provocation tests — including FABER, thigh thrust, Gaenslen’s test, compression, distraction, and sacral thrust — yields 91 percent sensitivity and 78 percent specificity for SI joint dysfunction, based on the Laslett study published in PMC. The FABER combined with thigh thrust has been identified as the most accurate two-test pairing. These are hands-on maneuvers that take minutes to perform and require no imaging equipment, yet they are frequently omitted from standard back pain evaluations. Compare this to the diagnostic approach for herniated discs, which relies heavily on MRI findings plus the straight leg raise test. The tradeoff is that MRI is excellent at showing structural disc pathology but poor at proving that the disc is actually the pain generator — disc bulges are notoriously common in pain-free individuals.
SI joint provocation tests, on the other hand, directly stress the joint in question and provoke the patient’s familiar pain if it is the source. The gold standard for confirming SI joint dysfunction is an image-guided diagnostic injection of local anesthetic directly into the joint. If the injection eliminates or substantially reduces the pain, the diagnosis is confirmed. No equivalent “litmus test” exists for disc pain with the same level of specificity. For families navigating this with a loved one who has cognitive impairment, advocate for these physical examination tests explicitly. A patient with dementia may not be able to articulate that the pain pattern changed after a straight leg raise versus a FABER test, but a skilled examiner can observe pain responses and guarding even in patients with limited verbal communication. Do not accept an MRI finding as the final word when the clinical picture does not match.
Pelvic Instability and Sleep Disruption — The Overlooked Red Flags
Two symptoms that are relatively specific to SI joint dysfunction but routinely overlooked are pelvic instability and positional sleep disruption. Pelvic instability manifests as a sensation that the pelvis will buckle or give way during standing, walking, or transitioning from sitting to standing. It is not the same as generalized weakness or balance problems from deconditioning or neurological disease. It is a mechanical feeling of the pelvis shifting, and patients who experience it often describe it as the sensation that something is “out of place” in their lower back or hip. This symptom is documented by Spine-Health as characteristic of SI joint dysfunction and is distinct from the radicular weakness that might accompany a severely herniated disc.
The warning here is that in older adults, especially those with dementia or other neurological conditions, pelvic instability from SI joint dysfunction can be misinterpreted as a gait or balance problem related to the neurological disease itself. A caregiver might attribute increased falls or reluctance to walk to disease progression when the actual cause is mechanical pelvic pain that could be treated. Sleep disruption from SI joint dysfunction presents a similar attribution problem. Chronic SI joint inflammation makes it difficult to find a comfortable sleeping position, with constant waking from lower back and buttock pain that closely mirrors disc-related night pain. Poor sleep accelerates cognitive decline, worsens behavioral symptoms in dementia, and exhausts caregivers. Identifying and treating the SI joint as the sleep disruptor can have cascading benefits that extend far beyond the back.
When Both Conditions Exist at the Same Time
Given that studies show 33 to 72 percent overlap between lumbar disc herniation and SI joint dysfunction, the possibility that a patient has both problems simultaneously is not an edge case — it is common. This dual diagnosis scenario is where treatment outcomes hinge most heavily on accurate assessment. Research published in PubMed found that when SI joint dysfunction was identified and treated in patients who also had disc herniation, 73.9 percent reported improvement, compared to only 54.8 percent of those whose SI joint dysfunction was not addressed.
That 19-point gap in outcomes represents a substantial number of patients who suffered unnecessarily because one of their two pain generators was ignored. For practical purposes, this means that even if disc herniation has been confirmed and even if some treatment directed at the disc has provided partial relief, it is worth pursuing SI joint evaluation if residual pain persists. The two conditions require different treatment approaches — epidural steroid injections and surgical decompression target disc pathology, while SI joint dysfunction responds to joint-specific injections, physical therapy focused on pelvic stabilization, and in refractory cases, SI joint fusion. Treating one while ignoring the other is a recipe for incomplete recovery.
Moving Toward Better Diagnostic Awareness
The trajectory of SI joint dysfunction recognition has been steadily improving, but the legacy of decades of neglect still shapes clinical practice. For most of the 20th century, the SI joint was dismissed as an immobile, irrelevant structure, and that institutional inertia means many practicing physicians completed their training without meaningful exposure to SI joint evaluation techniques. Awareness is growing, driven by the research cited throughout this article and by organizations like SI-BONE that have brought attention to the problem of SI joint misdiagnosis.
For patients and caregivers, the most productive step forward is informed self-advocacy. Knowing that SI joint provocation tests exist, that pseudo-sciatica has characteristic patterns, and that diagnostic injections can confirm the diagnosis gives you specific requests to bring to your provider. This is particularly important in the context of aging and cognitive decline, where undertreated pain erodes quality of life in ways that compound every other challenge a family is already managing.
Conclusion
SI joint dysfunction is one of the most commonly missed diagnoses in chronic low back pain, responsible for 15 to 30 percent of cases and coexisting with disc herniation at alarming rates. The eight symptoms it shares with herniated disc pain — one-sided lower back pain, pseudo-sciatica, groin pain, hip and pelvis pain, stiffness and reduced range of motion, leg numbness and tingling, pelvic instability, and positional sleep disruption — create a diagnostic trap that catches patients and clinicians alike. The tools to distinguish between these conditions exist: provocation testing, the straight leg raise, and image-guided diagnostic injections are all validated and accessible. If chronic back pain has not responded to disc-focused treatment, or if a loved one with cognitive impairment is declining in mobility and sleep quality without clear explanation, bring the SI joint into the conversation with their medical team.
Ask specifically about provocation testing. Ask whether a diagnostic injection is warranted. The research consistently shows that identifying and addressing SI joint dysfunction, even alongside existing disc pathology, substantially improves outcomes. This is not about replacing one diagnosis with another — it is about making sure nothing treatable is being missed.
Frequently Asked Questions
Can SI joint dysfunction cause sciatica that goes all the way down to the foot?
SI joint dysfunction typically produces pseudo-sciatica that radiates into the buttock and back of the thigh but does not extend below the knee. True sciatica from a herniated disc is more likely to travel to the foot. However, exceptions exist, and some SI joint patients do report lower leg symptoms, which is why physical examination tests and diagnostic injections are essential for accurate differentiation.
How do doctors confirm that the SI joint is the source of pain rather than a disc?
The gold standard is an image-guided diagnostic injection of local anesthetic directly into the SI joint. If the injection substantially reduces the patient’s familiar pain, the SI joint is confirmed as a pain generator. Additionally, a cluster of three or more positive SI joint provocation tests yields 91 percent sensitivity and 78 percent specificity for the diagnosis.
If I already had back surgery for a herniated disc and still have pain, could it be my SI joint?
Yes. In patients with failed back surgery syndrome, SI joint dysfunction is the pain source in up to 40 to 63 percent of cases. Many of these patients were originally treated for disc pathology without the SI joint ever being evaluated. Post-surgical SI joint assessment should be considered standard practice when pain persists after disc surgery.
Can someone have both SI joint dysfunction and a herniated disc at the same time?
This is not only possible but common. Studies show that 33 to 72 percent of patients with confirmed lumbar disc herniation also have co-existing SI joint dysfunction. When both are identified and treated, 73.9 percent of patients report improvement, compared to 54.8 percent when SI joint dysfunction is not addressed.
Is SI joint dysfunction more common in older adults?
SI joint dysfunction can occur at any age but becomes more prevalent with degenerative changes, osteoarthritis, and altered gait mechanics that accompany aging. In older adults, particularly those with reduced mobility or neurological conditions, the symptoms are more likely to be attributed to other causes, making clinical suspicion and appropriate testing especially important.
