The sacroiliac joint is responsible for up to a quarter of all chronic low back pain — yet it is one of the most frequently overlooked diagnoses. When SI joint pain is confirmed and conservative care has failed, minimally invasive fusion with FDA-cleared implants reliably stabilizes the joint and provides lasting relief, typically as an outpatient procedure.
The sacroiliac joints connect the sacrum — the triangular bone at the base of the spine — to the pelvis on each side. They transmit all the load from the upper body to the legs, absorb the forces of walking and movement, and are stabilized by some of the strongest ligaments in the body. When these joints degenerate, become inflamed, or lose stability, they can produce significant and often debilitating pain.
SI joint pain is commonly felt in the lower back, buttock, and sometimes the groin or thigh. It is often mistaken for lumbar disc disease or radiculopathy because the symptom patterns overlap. A key distinguishing feature is that SI joint pain tends to be provoked by prolonged sitting, transitional movements (rising from a chair, rolling over in bed), and activities that load one side of the pelvis asymmetrically. Radiation below the knee is less common than with true lumbar radiculopathy.
SI joint pain cannot be reliably diagnosed on MRI or CT alone — imaging findings in the joint often do not correlate with the degree of pain. Physical examination provocative tests (FABER, Gaenslen's, thigh thrust, and others) raise suspicion for SI joint involvement, but no single test is definitive. The gold standard for confirming the diagnosis is an image-guided SI joint injection.
A fluoroscopy- or CT-guided injection of local anesthetic directly into the SI joint confirms the diagnosis when it produces significant — typically greater than 75% — temporary relief of the patient's usual pain. This step is required before surgical planning and is also one of the initial treatment options, as corticosteroid injections can provide meaningful medium-term relief in many patients.
If you have had persistent low back and buttock pain despite lumbar-focused treatment, and your lumbar MRI does not explain your symptoms, an SI joint evaluation — beginning with a diagnostic injection — is worth discussing with your surgeon. The SI joint is the source of pain in an estimated 15–25% of patients with chronic low back pain, yet it is underdiagnosed in routine clinical evaluation.
Minimally invasive SI joint fusion is considered after conservative care has not provided lasting relief and the SI joint has been confirmed as the pain source by diagnostic injection. Most patients will have a meaningful trial of non-surgical management before surgery is discussed.
Minimally invasive SI joint fusion can be performed through three surgical approaches. The choice depends on patient anatomy, implant system used, prior surgery, and surgeon preference. All three achieve the same goal — stable arthrodesis of the SI joint — through small incisions without disrupting the lumbar musculature or spinal canal.
SI joint fusion has one of the fastest recovery profiles in spine surgery. Because the procedure is performed through a small lateral incision without disturbing the lumbar muscles or spinal canal, post-operative soreness is minimal and patients are ambulatory the same day.
Multiple prospective studies of FDA-cleared minimally invasive SI joint fusion systems show durable pain relief and functional improvement at two- and five-year follow-up in well-selected patients. As with all pain procedures, optimal outcomes depend on accurate diagnosis — which is why diagnostic injection confirmation is essential before surgery.
SI joint dysfunction is responsible for a significant portion of chronic low back pain — and is frequently overlooked. If your spine imaging doesn't explain your symptoms, an SI joint evaluation may provide the answer. Our surgeons will review your history and discuss whether diagnostic injection is the right next step.
SI joint fusion is used to treat confirmed sacroiliac joint dysfunction. If you have been diagnosed with one of the following — or have persistent low back or buttock pain without a clear lumbar explanation — SI joint evaluation may be the right starting point.
Our fellowship-trained spine surgeons will evaluate your symptoms, review your imaging, and determine whether SI joint evaluation — starting with a diagnostic injection — is the right next step.