SI joint dysfunction: the low-back pain that lives to one side.
A deep ache low and off to one side of your back — right over the dimple — that flares standing, rolling over in bed, or on the stairs. Why it is often the SI joint, not sciatica or a disc.
There is a low-back ache that sits low and off to one side, right over the little dimple above the top of your buttock. It tends to flare after you have been standing a while, when you roll over in bed, or when you climb a flight of stairs — and when someone asks where it hurts, you can usually point to the spot with one finger. That precise, one-sided, pointable pain has a clinical name most people have never heard until it lands on them: sacroiliac joint dysfunction, or SI joint dysfunction for short.
Why does my lower back hurt on one side?
Your sacroiliac joints are the two spots where the base of your spine — the triangular sacrum — meets the broad wings of your pelvis. There is one on the left and one on the right, and they sit almost exactly under those two dimples in your lower back. They are not built to move much; their job is to transfer the load of your upper body down into your legs and to absorb the twist of every step.
When one of those joints starts moving a little too much, a little too little, or simply gets irritated, the pain shows up on that one side and stays there. That is why SI joint pain almost never sits dead-center or spreads evenly across the whole low back — it picks a side. The Cleveland Clinic notes the SI joints are among the most common sources of low-back and buttock pain, yet they are one of the most frequently overlooked.
Is it SI joint pain, sciatica, or a disc?
This is the question that matters, because the three get confused constantly and they do not respond to the same treatment. True sciatica is a nerve problem — pain that starts in the low back and shoots down the leg in a line, often past the knee, sometimes with numbness or pins and needles in the foot. Disc pain usually hurts with bending forward, coughing, or sitting for long stretches, and it tends to sit more centrally or radiate down a specific nerve path.
SI joint dysfunction is different in feel. The ache is deep, dull, and anchored to one spot over the joint; if it refers into the leg at all, it usually stops at the back of the thigh rather than traveling all the way to the foot. The tells are mechanical: pain rolling over in bed, getting in and out of the car, standing on one leg to put on pants, or going up stairs — loads that ask a single SI joint to stabilize on its own.
Muscle-driven buttock pain is the fourth look-alike. A tight deep hip rotator can pinch the sciatic nerve and mimic all of this, which is exactly what we cover in our piece on piriformis syndrome. Sorting these four apart is a clinical exam, not a guess — which is the whole point of our pain locator and, more thoroughly, the in-person assessment.
When a patient can cover the sore spot with one fingertip and it sits right over the dimple, the SI joint just moved to the top of my list — no other low-back problem points to itself that cleanly.
What makes the SI joint start acting up?
The SI joint gets cranky when the load around it stops being shared evenly. Pregnancy is a classic trigger, because the hormone relaxin loosens the pelvic ligaments and one joint can start moving more than its partner. A hard fall onto one buttock, a misjudged step off a curb, or a stumble that jars the pelvis can do it in an instant.
More often, though, it builds slowly. A weak glute medius lets the pelvis drop and rotate with every step, and the SI joint on that side ends up absorbing forces it was never meant to carry alone. Repetitive one-sided loading — always standing on the same leg, always twisting the same direction, or grinding through a heavy day of lifting with a rounded low back — quietly overloads one joint until it protests.
How we pin down the SI joint at The Spine Studio
Here is where a lot of care goes sideways: a lumbar MRI comes back clean, the disc looks fine, and the patient gets told it is "non-specific low-back pain" and sent off with anti-inflammatories. But an MRI of the spine does not diagnose the SI joint — this is a joint that reveals itself through movement and hands-on testing, not a scan.
At The Spine Studio, Dr. Andersen works through a cluster of provocation tests — thigh thrust, compression, distraction, and the FABER position — that each load the SI joint in a different direction. When several of them reproduce that same one-sided pain over the dimple, and the neurological screen is clean (reflexes normal, no true nerve-path numbness), the picture points squarely at the joint rather than the disc or the nerve root. No single test is definitive; the pattern is.
What treatment actually looks like
Once the SI joint is confirmed as the driver, the plan is about restoring even, controlled load — not chasing the pain around. It usually blends a few of our core chiropractic services, matched to what the exam found.
- Precision Spinal Adjustments. A specific adjustment to the restricted SI joint restores normal motion and often takes the sharp edge off that same visit.
- Pin & Stretch and Cupping & Scraping. The muscles guarding the angry joint — glutes, deep rotators, low-back extensors — are usually locked down, and releasing them lets the correction hold.
- Corrective Exercise Programming. This is the part that actually keeps it gone. Rebuilding the glute medius and training the pelvis to stay level under load removes the one-sided overload that irritated the joint in the first place.
For a stubborn joint that has been inflamed for months, Shockwave Therapy — offered as a $375 three-session package, the minimum recommended course — can stimulate repair in the surrounding ligaments and tendons. Acupuncture is another option we reach for when the surrounding muscle guarding will not settle.
If your low-back pain lives over one dimple, flares rolling over in bed or climbing stairs, and your spine imaging came back clean, it is worth a proper SI joint exam. Dr. Andersen will test the joint directly rather than treating a scan that was never looking in the right place.
Our office sits in Cottleville, a short drive for patients across St. Charles County. Whether you are coming from O'Fallon, over from St. Peters, or in from St. Charles, the SI joint gets the same hands-on, rehab-focused workup — tested directly, adjusted, then loaded back to level so the fix holds.
One-sided low-back pain is rarely a mystery once someone tests the right joint. If yours has been shrugged off as "just low-back pain," a focused exam in Cottleville can name it — and once it has a name, it has a plan.
Get the joint tested directly, not guessed at from a scan.
Frequently asked questions
- Why does my lower back hurt on one side?
- One-sided low-back pain right over the dimple above the buttock is very often the sacroiliac (SI) joint, where the base of your spine meets the pelvis. Because that joint sits off to one side, its pain picks a side rather than spreading across the whole back. It tends to flare when you stand a while, roll over in bed, or climb stairs. A hands-on exam sorts it from sciatica, a disc, or a tight hip muscle, since a spine scan alone will not diagnose it.
- How is SI joint dysfunction different from sciatica?
- True sciatica is a nerve problem that shoots down the leg in a line, often past the knee, sometimes with numbness in the foot. SI joint dysfunction is a joint problem — a deep, dull ache anchored to one spot over the joint that, at most, refers into the back of the thigh. Sciatica flares with bending and sitting, while SI pain flares with single-leg loads like stairs and rolling in bed. The treatments are different, which is why getting the diagnosis right matters before you start.
- Can a chiropractor help SI joint dysfunction?
- Yes. A specific adjustment restores normal motion to the restricted SI joint, and soft-tissue work releases the muscles guarding it so the correction holds. The lasting fix is corrective exercise that rebuilds the glute strength and pelvic control that keep load even across both joints. At The Spine Studio in Cottleville, Dr. Andersen tests the joint directly rather than treating a scan that was never looking at it.
- Why did my MRI come back normal if my back still hurts?
- A lumbar MRI images the spine, discs, and nerve roots — it does not diagnose the sacroiliac joint. The SI joint reveals itself through movement and hands-on provocation testing, not a scan, so a clean MRI is common with SI joint dysfunction. That is exactly why so many one-sided low-back cases get mislabeled as non-specific pain. The answer is a clinical exam that loads the joint in several directions to see what reproduces your pain.
