Sacroiliac (SI) Joint Injection

You cannot tell for sure from symptoms or scans alone, partly because SI joint pain overlaps with pain from the lower spine and hip^[3]. Exam stress tests can point toward the joint, but evidence for imaging is unclear or negative^[1]. A numbing injection is the most direct test: if your usual pain drops sharply while the anesthetic works, the SI joint is a likely source.

An SI joint injection contains a local anesthetic, such as lidocaine or bupivacaine, usually with a corticosteroid, plus a little contrast dye so your physician can see the medicine spread inside the joint. A purely diagnostic injection may use only the anesthetic. Medicare’s policy for New York limits SI joint injections to an anesthetic, a corticosteroid and contrast^[2].

Most people describe brief pressure and aching rather than sharp pain. The skin is numbed first, and you may feel a familiar deep ache in the buttock as the medicine enters the joint, which usually fades within minutes. An SI joint nerve block involves several small needle placements and can feel a little more uncomfortable. Little or no sedation is used, so you can judge your relief.

They help many well-selected patients, at least for a while. The 2025 multispecialty guidelines found that steroid injections inside and around the SI joint gave at least four weeks of relief in well-selected patients, although overall evidence quality was low^[1]. Injections also work as a test: strong relief while the anesthetic is active points to the SI joint and guides next steps.

The numbing medicine lasts a few hours. Steroid relief, if it comes, usually begins within a few days and varies in length; the guidelines report at least four weeks in well-selected patients^[1]. Medicare covers repeat injections only when each gives at least 50% relief lasting three months or more^[2] — a useful benchmark for whether repeating makes sense.

An SI joint injection places medicine inside the joint to test for, or treat, pain coming from within it. An SI joint nerve block, or sacral lateral branch block, numbs the small nerves serving the ligaments at the back of the joint and is mainly a test before SI joint radiofrequency ablation^[1]. Nerve blocks do not reliably numb the inside of the joint^[5].

Tell us about all your medicines, especially blood thinners. SI joint injections are considered low bleeding-risk procedures, so many patients can continue their medicines^[6] — but never stop or change one without your prescribing doctor. Tell us about diabetes, contrast allergies or possible pregnancy^[7], and arrive with your usual pain so you can compare before and after.

Most people go home the same day and resume normal activities the next day. For several hours, try activities that usually hurt and note your pain — this tells your physician whether the test was positive. The leg on the treated side can feel briefly numb or weak, so do not drive until it feels normal. Soreness for a day or two is common.

Serious complications are uncommon. The most common effects are temporary soreness, a brief pain flare and short-lived leg numbness. As with other spinal injections, light-headedness, headache, infection and nerve injury are possible but uncommon, and the steroid can briefly raise blood sugar^[7]. Because X-ray is used, tell us if you might be pregnant.

Only as often as they clearly help. Medicare’s policy for New York allows up to two diagnostic sessions and up to four therapeutic sessions in a rolling 12 months, each repeat requiring at least 50% relief or improved function for three months^[2]. New York workers’ compensation guidelines do not recommend more injections unless the first ones brought significant improvement^[7].

If you get no relief even while the anesthetic works, the pain may come from elsewhere, such as the facet joints, the hip or a pinched nerve. If relief is real but brief, options include SI joint radiofrequency ablation after nerve blocks or, for carefully selected people, SI joint fusion, for which the evidence is weaker^[1].

Medicare and most commercial plans cover image-guided SI joint injections when criteria are met. Medicare’s policy for New York requires at least three months of pain, four weeks of conservative care, three positive exam tests and image guidance with contrast; it does not cover SI joint radiofrequency ablation^[2]. Commercial plans often need prior authorization, and workers’ compensation and no-fault follow their own rules^[7].