In short — Sacroiliac (SI) joint pain often causes low back, buttock, or hip pain that can feel similar to disc or facet pain. It tends to worsen with standing, transitional movements, or one-sided activity. Diagnosis is usually confirmed with a focused exam and a diagnostic SI joint injection, not imaging alone, before treatment is planned.
A patient may have already tried physical therapy, a course of medication, and even an epidural steroid injection for "back pain" that never fully improved. The MRI looked reasonable. The disc did not seem severe enough to explain the symptoms. Nothing quite fit.
In some of these patients, the pain was never coming from the spine itself. It was coming from the sacroiliac joint — the joint that connects the base of the spine to the pelvis on either side.
Patients across Jacksonville, Mandarin, Southside, Orange Park, St. Johns, Ponte Vedra, and the rest of Northeast Florida often describe this same frustrating pattern: pain that is real, that limits standing and walking, and that does not match what the imaging seems to show.
What the SI joint is and why it can hurt
The sacroiliac (SI) joints sit on either side of the low back, where the sacrum meets the ilium of the pelvis. They carry load between the spine and the legs and allow small amounts of motion that help absorb stress during walking, standing, and transferring weight from one leg to the other.
When an SI joint becomes irritated, inflamed, or unstable, it can become a source of persistent low back, buttock, or hip pain. Causes can include a fall or direct impact, pregnancy-related changes, prior lumbar fusion that shifts stress onto the joint, degenerative arthritis, or repetitive asymmetric loading.
Symptoms that point toward the SI joint
SI joint pain often localizes near a dimple on one side of the low back, just above the buttock, and it may spread into the buttock, groin, or upper thigh. Pain that travels clearly below the knee in a nerve-like pattern is less typical of the SI joint and more suggestive of a nerve-root problem.
Patients commonly notice pain with standing up from sitting, rolling over in bed, climbing stairs, standing on one leg to put on pants or shoes, or sitting for long periods on a hard surface. Pain is often worse on one side and can feel like a deep ache rather than a sharp or burning nerve sensation.
Why the diagnosis is easy to miss
A common misconception is that a normal-looking MRI means there is nothing structurally wrong. That is not always true for the SI joint. Imaging can show mild arthritis, sacroiliitis, or asymmetry, but it can also look unremarkable even when the joint is contributing meaningfully to a patient's pain.
Because low back, buttock, and hip pain can come from the spine, the hip joint, the SI joint, or surrounding muscles, symptoms can overlap significantly. That overlap is part of why SI joint pain is often treated as ordinary low back pain for months or years before it is specifically evaluated.
How the diagnosis is confirmed
Confirming the SI joint as a pain generator typically starts with a history and a focused physical exam, including specific provocative maneuvers that attempt to reproduce the patient's usual pain by stressing the joint.
Because exam findings and imaging alone are not always definitive, a diagnostic SI joint injection is often the most reliable next step. A small amount of numbing medication is placed into the joint under image guidance. If the injection substantially and temporarily relieves the patient's usual pain, that response supports the SI joint as a likely source and helps guide the treatment plan.
What this means for patients
If you have been told your imaging is "fine" but your low back and buttock pain has not improved with typical treatment, it may be worth asking whether the SI joint has been specifically evaluated. This is not about assuming every case of stubborn low back pain is the SI joint — it is about not skipping a joint that is easy to overlook.
A careful evaluation also helps rule out other explanations, including hip arthritis, facet joint pain, lumbar radiculopathy, and, less commonly, inflammatory conditions that can involve the SI joints on both sides.
When symptoms should not wait
Most SI joint-related pain is not an emergency, but some symptoms deserve prompt evaluation.
Seek urgent medical care for new leg weakness, loss of bowel or bladder control, numbness in the groin or saddle area, fever with spine or joint pain, significant trauma, or rapidly worsening pain. Those symptoms should be evaluated promptly rather than managed at home.
Treatment options, depending on the diagnosis
Treatment depends on the diagnosis, exam findings, imaging, prior care, and patient goals. Conservative care often comes first and may include activity modification, targeted physical therapy focused on pelvic and core stability, and a review of medications.
In selected patients, a therapeutic SI joint injection may reduce inflammation and pain, sometimes doing double duty as both a diagnostic and a temporary therapeutic step. If pain responds well to diagnostic blocks but keeps returning, radiofrequency ablation of the small nerves supplying the joint may be considered to calm pain signals for a longer period.
For patients with confirmed, disabling SI joint dysfunction that has not improved with appropriate non-surgical care, minimally invasive SI joint fusion may be discussed. This is reserved for carefully selected patients after the diagnosis has been confirmed with diagnostic injections; it is not an early or default option.
Questions to ask your physician
Useful questions include:
- Does my pain pattern and exam fit the SI joint, the hip, a nerve root, or more than one source?
- Would a diagnostic SI joint injection help confirm or rule out the joint as a pain generator?
- What would meaningful relief from that injection tell us about next steps?
- What non-surgical options make sense before considering a procedure?
- What symptoms would mean I should seek care sooner rather than waiting?
The bottom line
Not every stubborn case of low back pain is a disc problem, and a reassuring MRI does not always mean the SI joint has been ruled out. Pain pattern, physical exam, and, when appropriate, a diagnostic injection often matter more than imaging alone.
Getting the diagnosis right first can help avoid treating the wrong pain generator and can point toward a plan that actually fits the problem.
This article is for general educational purposes only and is not a substitute for a medical evaluation. If you have new weakness, loss of bowel or bladder control, fever, major trauma, severe worsening pain, or other urgent symptoms, seek medical care promptly.
Frequently Asked Questions
How do I know if my low back pain is coming from my SI joint?
SI joint pain often sits low, near a dimple on one side of the low back, and may spread into the buttock, groin, or upper thigh. It can worsen with standing from sitting, rolling in bed, climbing stairs, or standing on one leg. A focused exam and diagnostic injection help confirm the source.
Can an MRI show sacroiliac joint pain?
Sometimes, but often not clearly. Imaging may show mild arthritis, sacroiliitis, or nothing remarkable even when the joint is a significant pain generator. Diagnosis usually relies on the exam and how a diagnostic injection responds, not imaging alone.
What is a diagnostic SI joint injection?
It is an image-guided injection of numbing medication into the sacroiliac joint. If it substantially and temporarily relieves the usual pain, that response supports the SI joint as a likely pain generator and helps guide further treatment.
Is sacroiliac joint pain the same as sciatica?
No. Sciatica usually involves a nerve root pattern that travels below the knee. SI joint pain more often stays in the low back, buttock, groin, or upper thigh, though the two can sometimes be confused or coexist.
What treatments may help SI joint pain?
Depending on the diagnosis, options may include activity modification, physical therapy focused on pelvic stability, medication review, SI joint injections, radiofrequency ablation of the nerves supplying the joint, or, in selected patients with confirmed dysfunction, SI joint fusion.
Related patient education
- Is it sciatica? How pain patterns guide the next step
- Why MRI results may not fully explain pain
- When radiofrequency ablation may fit facet-related back or neck pain
- Preparing for an interventional pain procedure
Related services
- Back pain diagnosis and treatment options
- SI joint fusion (sacroiliac arthrodesis)
- Radiofrequency ablation service overview
- Sciatica and radiating leg pain care
Wondering if your pain is coming from your SI joint?
A careful evaluation can help determine whether symptoms fit the SI joint, the spine, the hip, or a mixed pattern.
Contact the office about an appointment