The lower-back pain that isn't your spine.
SI joint pain is one of the most underdiagnosed causes of lower-back and buttock pain — often mistaken for a disc problem or hip arthritis for years. When you treat the right structure, the difference can be dramatic.
Your doctor may call this sacroiliac joint dysfunction or sacroiliitis.
Often seen within a few days — sometimes as soon as tomorrowRequest your first visit
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What si joint pain really is.
The sacroiliac joints sit at the base of the spine, connecting the sacrum (the triangular bone at the bottom of your back) to the iliac bones of the pelvis — one on each side. They're designed to transfer load between the spine and legs, and they don't move much. But when they're inflamed, stiff, or moving asymmetrically, they produce a characteristic pattern of pain: deep in the lower back or buttock, sometimes radiating into the hip or back of the thigh.
SI joint pain is estimated to account for 15–25% of chronic lower-back pain cases, yet it's frequently missed because it closely mimics disc and nerve problems on imaging. The sacroiliac joint doesn't show up well on the MRI views typically ordered for lower-back pain, and there's no single exam finding that confirms it — which is why clinical pattern recognition and a targeted diagnostic injection are often the most reliable path to a correct diagnosis.
The good news
Once the SI joint is confirmed as the pain source, treatment is often highly effective. Image-guided injections provide significant relief for most patients, physical therapy to restore pelvic mechanics helps prevent recurrence, and for those who need something more durable, minimally invasive SI joint fusion is an established option.
Distinguishing SI joint from lumbar pain
The FABER and Gaenslen provocative tests can raise clinical suspicion, but a fluoroscopy-guided SI joint injection delivering local anesthetic is the gold standard for confirming the joint as the pain generator. A ≥75% reduction in pain after injection is diagnostic. Without that confirmation, treatment is often directed at the wrong structure.
Common signs we treat.
Pain in the lower back or buttock
A unilateral (one-sided) ache in the very lower back, just above the tailbone or deep in the buttock — often worse on one side, and worsened by prolonged standing, climbing stairs, or lying on that side.
Pain into the hip or thigh
Pain that travels from the buttock into the outer hip or back of the thigh — but usually stops above the knee, which helps distinguish it from true sciatica that runs further down the leg.
Sharp pain rising from sitting
A sudden, sharp jolt of pain when standing up from a chair or getting in and out of a car — one of the most characteristic and frustrating patterns of SI joint involvement.
From hurting to healed.
We work from the least-invasive options upward, escalating only if you need it. Most patients improve well before surgery is ever discussed.
Diagnose the cause
A physician examines you and, if needed, reviews imaging to pinpoint exactly what's driving the pain.
Calm it down
Targeted physical therapy, activity guidance, and medication to settle the irritation and reduce inflammation.
Image-guided injections
If pain persists, a precisely targeted injection delivered to the source under imaging.
Advanced options
For the few who need more, minimally invasive interventional procedures — with surgery as a last resort.
Treatment is matched to your specific diagnosis at your visit. The options shown reflect NASPAC's general approach and should be confirmed against the practice's verified procedure list.
Still have questions?
The sacroiliac joints are located at the very base of the spine, on either side of the sacrum — you can roughly locate them by finding the dimples at the top of the buttocks. There are two: one on the left and one on the right. Pain from the SI joint is usually felt on one side, below the beltline and into the buttock.
Diagnosis combines the clinical pattern — where the pain is, what aggravates it, whether it radiates, and how it responds to specific exam maneuvers — with a fluoroscopy-guided diagnostic injection. If injecting the joint with local anesthetic produces a substantial, temporary reduction in your pain, that confirms the SI joint is the source. This is more reliable than MRI alone for SI joint pain.
An SI joint injection delivers corticosteroid and local anesthetic directly into the joint using X-ray guidance to confirm needle placement. It reduces joint inflammation, provides meaningful pain relief for weeks to months, and also serves as the definitive diagnostic test. Most patients tolerate it well and notice improvement within a few days to a week.
The SI joint is part of the pelvis, not the spine itself, but it sits right at the junction between them — which is why SI joint pain and lumbar spine pain feel so similar and so often coexist. A disc herniation or facet problem and SI joint dysfunction can be present at the same time, so a thorough evaluation distinguishes the contributions of each rather than assuming one diagnosis explains everything.
Stop living with the SI joint pain.
Book with a board-certified pain physician near you — most patients are seen within days.
Book an appointment → Or call (855) 862-7767