SI Joint Radiofrequency Ablation

Medically reviewed by Joshua L. Hare, DO, Founder & Medical Director

Conditions Treated

Chronic SI joint pain confirmed by diagnostic SI joint injections, sacroiliitis, SI joint dysfunction

SI Joint Radiofrequency Ablation at a Glance

Type of procedure	Outpatient, image-guided (fluoroscopy)
Anesthesia	Local anesthetic at the skin over each target point
Time in the procedure room	About 30–45 minutes
Back to normal activity	Within a few days
Relief typically develops	Over 2–4 weeks, with a sore stretch first for many patients
Relief typically lasts	Months — in the randomized trial, 57% of treated patients still had at least half their pain relieved at six months[1]
Repeatable	Yes — the lateral branches grow back over time, and a repeat is considered once relief has clearly faded

Where SI Joint Pain Is Felt

The sacroiliac joint sits where the base of the spine meets the pelvis, and pain from it is a bigger contributor than most patients expect — it accounts for roughly 20% of chronic low back pain.[1] It is also a mimic. One study logged 18 different referral patterns[2] from this joint: half of patients felt it down the back or side of the thigh, 28% below the knee, and 14% all the way into the foot — patterns easy to mistake for sciatica. That overlap is why the diagnosis is made with an image-guided test injection rather than by symptoms alone.

How It Works

After diagnostic SI joint injections confirm the pain source, radiofrequency probes are placed along the lateral branch nerves[2] under fluoroscopic guidance. Cooled radiofrequency technology creates larger, more consistent lesions for better nerve coverage.

The anatomy explains the approach. The back of the joint is served by the lateral branches of the S1–S4 nerve roots[2] — small sensory branches whose exact course varies from person to person. That variability is why the reference literature notes the ablation area increases with bipolar and cooled radiofrequency devices:[2] a wider lesion covers the spread of nerve positions a standard probe can miss. In the randomized trial of this procedure, the treated targets ran from the L4–L5 primary dorsal rami down the S1–S3 lateral branches.[1]

Who It Helps — and Who It Does Not

Candidacy starts with the test injection: this procedure treats only SI joint pain that injection has already confirmed. An image-guided injection is the gold standard for identifying sacroiliac joint dysfunction[2] — pain relief while the local anesthetic works is what confirms the joint, and a diagnostic SI joint injection comes before any ablation at IPC. If your test injection did not relieve the pain, the joint is the wrong target and ablating its nerves would treat the wrong structure.

One limit: denervation reaches the joint's posterior nerve supply, and does not address the anterior nerves.[2] Pain arising mostly from the front of the joint can persist after a technically perfect procedure — another reason the test-injection step matters.

The Day of the Procedure

1. Check-in and positioning. You lie face down while the low back and upper buttock are cleaned and draped; monitoring runs throughout.
2. Numbing. Each planned point along the sacrum is numbed at the skin, one at a time.
3. Guided placement. Radiofrequency probes are advanced to the lateral branch targets one by one under fluoroscopy, each position confirmed on the image.
4. Treatment. Each confirmed point is lesioned in turn. Because several small branches serve the joint, more points are treated than in most other ablations — the 30–45 minutes goes into that coverage.
5. Recovery and discharge. Discharge is same-day: a short stay in the recovery area, then home with written aftercare.

What the Evidence Shows

The controlled evidence comes from a randomized, placebo-controlled trial of cooled-probe lateral branch denervation. At one, three and six months, 79%, 64% and 57% of treated patients had pain relief of 50% or greater with significant functional improvement;[1] in the placebo group, 14% improved at one month and none were still better at three. The same trial followed patients out to a year, and the authors' conclusion was intermediate-term pain relief in selected patients,[1] which is why the at-a-glance table above counts in months, not years. The broader reference summary of the injection-then-denervation pathway: the majority of patients can achieve adequate pain relief[2] with these techniques.

Recovery, Week by Week

First 48 hours	Soreness is expected — the sacrum takes more treated points than most ablations. Ice and the discharge sheet cover the first two days.
Weeks 1–2	Expect a sorer stretch before improvement; that is the nerves reacting to the lesion, and it settles.
Weeks 2–4	Relief tends to arrive gradually across these weeks; most patients have long since returned to daily activity.
The months after	The lateral branches eventually grow back. If the pain returns, a repeat ablation can be scheduled — your follow-up visit is where that gets decided.

Risks and Side Effects

The expected side effect is the temporary soreness above. The reference literature lists few risks beyond that soreness: denervation may cause numbness[2] over the treated area, and electrode position is the safety-critical step, so placement is confirmed on fluoroscopy at every target point. Sacroiliac joint pain itself, like most mechanical low back pain, carries a good prognosis.[2]

The Test Injection and the Ablation: Which Is Which

SI joint injection	Local anesthetic (often with steroid) delivered into or around the joint itself. Its first job is diagnostic: relief while the anesthetic works confirms the joint as the pain source. See sacroiliac joint injection.
SI joint radiofrequency ablation	Heat treatment of the small nerve branches behind the joint. This is the therapeutic half — relief that holds for months, with a repeat possible as the branches regenerate.

Common Questions

Why do I need an injection before the ablation?

The injection is how the diagnosis is made: image-guided injection is the gold-standard test for SI joint pain, and relief while the anesthetic works is the evidence that this joint — not a disc, facet or nerve root — is generating your pain. Skipping it risks treating nerves that were never the problem.

My pain runs down my leg. Is that not sciatica?

Sometimes it is — and sometimes it is the SI joint mimicking sciatica. Half of patients in one referral-pattern study felt SI pain down the thigh, and 28% below the knee. The test injection is how the two are told apart, because a pinched nerve root does not improve when the SI joint is numbed.

What is “cooled” radiofrequency?

A probe design that circulates fluid to keep the tip cooler while heating a larger volume of tissue around it. For this joint that matters: the target branches vary in position from person to person, and the larger lesion covers that spread.

What happens when the relief wears off?

The treated branches regenerate, so relief fading over months is expected rather than a failure. If the same pain pattern returns and you had a good run of relief, repeat ablation is on the table — that conversation starts with how long the first one held.

References

Clinical sources for this page.

1. Cohen SP, Hurley RW, Buckenmaier CC 3rd, et al. Randomized placebo-controlled study evaluating lateral branch radiofrequency denervation for sacroiliac joint pain. Anesthesiology. 2008;109(2):279–288. Back to first citation ↑
2. Sacroiliac Joint Pain. StatPearls [Internet], National Library of Medicine; updated August 14, 2023. Back to first citation ↑