What is actually happening

The sacroiliac joint links the base of your spine to your pelvis on each side, absorbing shear force every time your weight shifts from one leg to the other. Two biological problems drive most of its pain: mechanical strain of the ligaments that stabilize it, from a fall, a twist, or years of asymmetric loading; and a genuinely inflamed joint capsule, which behaves like any other irritated synovial joint. A third, behavioral driver is common and underappreciated — standing on one leg to load a car, favoring a surgical hip, or a job with repeated stair or ladder work all put uneven shear through this joint day after day, which is why the pattern often builds slowly rather than announcing itself with one injury.

Below the belt line

Sacroiliac pain sits low, over the dimples just above the buttock on one or both sides, and can refer into the groin or down the back of the thigh, occasionally past the knee, which is why it is frequently mistaken for sciatica. The clue that separates it is behavioral, not anatomic: pain that is sharply worse rolling over in bed, standing up from sitting, or getting out of a low car, and that localizes when you point with one finger rather than sweeping a hand across your whole low back. Lumbar spine pain rarely does either of those two things this specifically.

Who this shows up in

And the pelvis in a car accident: a side-impact or rear-end collision loads the sacroiliac joints directly through the seat and seatbelt, and this practice sees it regularly along the Woodson corridor after a crash on I-70 — pain that gets attributed entirely to the lumbar spine because that is what the initial imaging targeted, while the joint below it was never examined.

Provocation testing, and its limits

No single physical exam maneuver is reliable alone, but clustering several — compression, distraction, thigh thrust and a few others — performs meaningfully better. A 2021 systematic review and meta-analysis in the Journal of Orthopaedic & Sports Physical Therapy found that a positive cluster of three or more provocation tests has real diagnostic value, while any single test used alone does not. That is why the exam here is a set, not one maneuver, and why a positive cluster earns a confirmatory injection rather than a diagnosis on its own.

A cluster of three or more positive provocation tests, not any single test alone, is what makes the sacroiliac joint a credible suspect.

Confirming it with an image-guided injection

Because the joint sits deep and its surface is irregular, it cannot be reached reliably by feel. A sacroiliac joint injection placed under fluoroscopic or ultrasound guidance, with contrast confirming the needle is actually inside the joint before medication is given, is both the diagnostic step and, often, an early therapeutic one. A 2025 multispecialty consensus guideline on sacroiliac joint complex pain lists image-guided intra-articular injection as the standard confirmatory test once a provocation cluster and history point here.

Lateral branch RF as the durable answer

For a confirmed joint, cooled radiofrequency ablation of the lateral branch nerves supplying it can hold relief for many months at a time. A 2024 multicenter randomized comparative-effectiveness trial in Regional Anesthesia and Pain Medicine found cooled RFA meaningfully outperformed standard medical management for chronic sacroiliac joint pain, which is the evidence base this practice is working from when it moves a confirmed patient from injection to radiofrequency ablation rather than repeating injections indefinitely.

Where surgery fits, and where it does not

For confirmed sacroiliac joint pain, surgery is not part of the treatment plan this practice builds — image-guided injection and lateral branch radiofrequency ablation are the interventional pathway offered here, and most confirmed patients get durable relief from that pathway without ever needing an operation. Sacroiliac joint fusion exists and is appropriate for a subset of patients whose pain keeps returning despite repeated, successful radiofrequency treatment; where that is the situation, it is a conversation for a surgical partner, coordinated from here, not a procedure performed in this office.

Red flags, in plain terms

Common questions

Related reading

• Sacroiliac joint injection
• Radiofrequency ablation
• Sciatica
• Failed back surgery syndrome
• After a car accident