SI joint dysfunction.
You can cover it with one finger. Low, to one side, just below the belt — and it hates rolling over in bed.
The joint that gets misdiagnosed as sciatica.
The sacroiliac joints sit where the sacrum — the triangular bone at the base of the spine — meets the pelvis on each side. They are built for stability rather than motion, moving only a few degrees. Their job is transferring load between your spine and your legs, absorbing the forces of every step you take.
When one of these joints stops moving and loading normally, it produces a distinctive pain: low on one side of the back, below the belt line, often pointed to with a single finger. It can refer into the buttock and the back of the thigh, which is precisely why it is so frequently mistaken for sciatica.
The distinction matters because the treatments differ. Sciatica from a lumbar disc means a nerve root is compressed, and the plan targets disc pressure. SI dysfunction is a mechanical load-transfer problem at the pelvis, and the plan targets joint motion and pelvic stability. Treating one as the other is a common reason low back pain fails to respond.
At our Jacksonville and Orange Park offices, the evaluation uses specific provocation tests that load the SI joint independently of the lumbar spine, so we can establish which structure is actually producing your symptoms before treating anything.
Does this sound familiar?
Restore the motion, then stabilise it.
Why it gets confused with sciatica so often
Both produce pain in the buttock. Both can refer down the back of the thigh. Both are worse with certain positions and better with others. From the patient's description alone they can be almost indistinguishable, and buttock pain is one of the most commonly misattributed symptoms in musculoskeletal practice.
The separations that matter clinically: true sciatica follows a nerve distribution and frequently includes numbness, tingling, or weakness, often extending below the knee. SI joint pain concentrates at the joint, refers more diffusely, and rarely produces genuine neurological signs in the lower leg.
Examination settles it. Specific provocation tests load the SI joint while sparing the lumbar spine, and neurological testing establishes whether a nerve root is actually involved. Where several provocation tests reproduce your pain and the neurological exam is clean, the SI joint is the likely source.
The hip connection
Recurrent SI joint problems very often have a stiff hip sitting underneath them. The pelvis and hip work as a unit, and when the hip loses rotation the pelvis compensates by moving more than it should.
Since the SI joint is built for stability rather than movement, being asked to supply motion it was not designed for is a reliable route to irritation. Treating the SI joint repeatedly while leaving the hip restricted is a cycle patients often describe — it helps each time and comes back each time.
This is why the assessment includes hip range of motion even when the complaint is squarely in the low back, and why restoring hip mobility is frequently what breaks the recurrence pattern.
Pregnancy and pelvic girdle pain
Pregnancy changes the pelvis in two relevant ways. Hormonal shifts increase ligament laxity to allow accommodation for delivery, and the growing centre of mass changes how load transfers through the pelvic ring.
The result is that pelvic girdle pain involving the SI joints is common in pregnancy, and it often behaves slightly differently — more likely to be bilateral, and more likely to be about too much motion rather than too little.
Treatment adapts accordingly: less emphasis on mobilising, more on stabilisation, support, and load management strategies. We provide pregnancy-adapted chiropractic care and modify technique and positioning throughout.
What makes it stay fixed
Restoring motion at a restricted SI joint often produces quick relief, which is satisfying and also slightly misleading. If nothing else changes, the same pattern tends to re-establish itself.
Durability comes from the stabilising system — gluteal strength, deep abdominal control, and the coordination between them — plus removing the drivers that overloaded the joint in the first place, most often a stiff hip or a habitual asymmetric loading pattern.
That is why the plan does not stop when the pain does. A pelvis that is comfortable but still poorly controlled is a pelvis that will be back.
Common questions about SI joint pain
Find out if it is the joint or the nerve.
SI dysfunction and sciatica feel similar and need different treatment. The examination separates them. Jacksonville and Orange Park.
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