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Key points
- A sacroiliac joint injection puts a small dose of steroid, local anaesthetic or both into the joint between the base of your spine and your pelvis, using live X-ray to guide the needle.
- The injection itself takes a few minutes and most people go home within a couple of hours.
- BASS reports that when the joint has been confirmed as the source of pain beforehand, more than 85 to 90 in 100 people gain a significant benefit, although how long it lasts varies a great deal.
- It works best as a window of relief that lets you exercise and rebuild strength, rather than as a treatment on its own.
- Serious problems are uncommon. The main risks are bleeding, infection and short-lived side effects from the steroid.
What is the sacroiliac joint?
You have two sacroiliac joints, one on each side of the lower back. Each links the sacrum, the triangular bone at the base of the spine, to the iliac bone of the pelvis. They work as shock absorbers, passing the weight of your upper body down into your legs when you stand and walk. Like any joint, they can wear and become arthritic, move too much or too little, or be injured.[1]
Pain sits low in the back and buttock and can spread into the groin or down the back of the thigh, much like hip or lumbar spine pain. Our guide to sacroiliac joint pain covers the condition in more detail.
What the injection aims to do
The injection delivers an anti-inflammatory steroid, often mixed with local anaesthetic, directly into the joint.[1] The local anaesthetic numbs the area for a few hours. If your usual pain fades noticeably during that time, it adds weight to the idea that the joint is the source, which is why these injections are sometimes described as both a test and a treatment. The steroid works more slowly, and BASS notes that the full benefit can take several weeks to appear.[1]
The aim is not to cure the joint. It is to settle the pain enough for you to start a programme of stretching and strengthening, which BASS suggests beginning about a week after the injection.[1]
Who it is for, and the alternatives
An injection is usually considered when pain from the joint has gone on for some time and is getting in the way of everyday life, despite simpler measures such as pacing your activity, painkillers and physiotherapy.
You may read differing views about spinal injections. NICE guideline NG59, which covers low back pain and sciatica, advises against offering spinal injections for managing low back pain in general.[2] It does not single out the sacroiliac joint, and specialists still use targeted injections when the history and examination point to that joint. A systematic review by Kennedy and colleagues found that only around 20 to 30 in 100 people suspected of sacroiliac pain turn out to have pain coming from the joint, which shows how tricky the diagnosis can be. The same review rated the overall evidence for therapeutic joint injections as moderate.[3]
Other options include continuing an exercise-based rehabilitation programme, radiofrequency denervation (heat applied to the small nerves that carry pain signals from the joint) and, for a small number of people with persistent severe pain, surgery to fuse the joint.[1] If your pain is mainly from the small facet joints of the spine instead, a facet joint injection may be more appropriate.
Before the injection
- Tell your consultant if you take a blood thinner such as warfarin, rivaroxaban or clopidogrel, as you may need to stop it beforehand. If your appointment comes at short notice, check straight away which medicines to pause so the injection isn’t postponed.[1]
- Mention any skin problem on your lower back, such as psoriasis or eczema, because it can raise the chance of infection.[1]
- If you have diabetes, be ready to check your blood sugar more often for a few days afterwards.
- If you are having sedation, arrange for an adult to take you home and stay with you overnight.[1]
- Keep taking your usual painkillers. Never stop strong painkillers or nerve pain medicines such as gabapentin, pregabalin or amitriptyline suddenly; your GP can help you reduce them gradually later on.[1]
On the day
Depending on your hospital, the injection is done either under local anaesthetic, which numbs the skin and tissues, or with intravenous sedation so that you are asleep. You lie on your front on a couch, usually resting your head sideways on a pillow. The skin is cleaned with antiseptic, and live X-ray is used to steer a fine needle into the joint. Once it is in the right place, a small volume of steroid and local anaesthetic is injected. The whole thing usually takes just a few minutes.[1]
Arthritis sometimes causes bony outgrowths around the joint that make it hard to get the needle right into the joint space. BASS notes that the pain relief may then be less effective.[1]
After the injection
A nurse will check your pulse and blood pressure in the recovery area. Most people go home within a couple of hours, once they are up and walking.[1]
- After sedation, don’t drive for 48 hours, and have a responsible adult with you overnight.[1]
- You may want the next day off work, longer if your pain is slow to settle. The hospital or your GP can provide a fit note.[1]
- Carry on with your usual pain relief until the steroid begins to help.[1]
Getting back to exercise
BASS recommends starting a gentle exercise programme about a week after the injection.[1] Its booklet includes simple stretches and strengthening moves for the thighs, buttocks and trunk, which a physiotherapist can tailor to you.
Risks and complications
Risks are few. BASS does not give numerical rates for this procedure, so the table uses its descriptions.[1]
| Risk | How common (BASS) |
|---|---|
| Bleeding | Very uncommon. More likely if you take blood thinners |
| Infection | Rare. Skin conditions on the back raise the risk |
| Facial flushing | Short-lived, caused by the steroid |
| Changes to periods, or bleeding after the menopause | Short-lived, caused by the steroid |
| Raised blood sugar in people with diabetes | Lasts a few days |
| Needle unable to enter the joint fully because of bony outgrowths | Sometimes. Pain relief may then be less effective |
How well does it work?
BASS reports that when sacroiliac pain has been confirmed beforehand, more than 85 to 90 in 100 people get a significant benefit. How long it lasts is unpredictable: a few weeks for some, months or even years for others.[1]
The research picture is less clear-cut. Kennedy’s review found that 2 randomised trials and several observational studies supported therapeutic injections, but it was unclear whether a good response to a numbing test injection predicts a good response to steroid.[3] A 2026 network meta-analysis by Park and colleagues pooled 18 randomised trials with 1,075 patients. Radiofrequency treatments generally gave better pain relief than steroid injections, sham procedures or conservative care, though the authors rated the certainty of the evidence as low to very low.[4] NICE’s recommendation on radiofrequency denervation covers pain thought to come from structures supplied by the medial branch nerves, which serve the facet joints, rather than the sacroiliac joint.[2]
If the first injection helped, it can often be repeated, but most specialists wait at least six months. If things have not improved by six weeks, or relief was brief, the next step may be referral to a pain clinic to look at other options, which can include radiofrequency denervation. Surgery to fuse the joint is usually only considered when injections, physiotherapy and denervation have not helped.[1]
When to seek help
Contact the hospital or your GP if the injection site becomes red, hot, swollen or starts to leak, if you develop a temperature, or if your blood sugar stays high for more than a few days.
Seek urgent medical help (A&E or 999) if you have:
- Severe, worsening back pain with a fever or feeling generally very unwell
- New numbness around your bottom, genitals or inner thighs
- New difficulty passing urine, or loss of control of your bladder or bowels
- New weakness in one or both legs (these last three can be signs of cauda equina syndrome)
Further reading
References
- British Association of Spine Surgeons. Sacroiliac joint pain: injection treatment (patient booklet, issue 1). BASS; 2022. Link
- National Institute for Health and Care Excellence. Low back pain and sciatica in over 16s: assessment and management (NG59). NICE; 2016, last updated 2026. Link
- Kennedy DJ, et al. Fluoroscopically guided diagnostic and therapeutic intra-articular sacroiliac joint injections: a systematic review. Pain Med. 2015;16(8):1500-18. Link
- Park JH, et al. Interventional treatments for sacroiliac joint pain: a systematic review and network meta-analysis. Reg Anesth Pain Med. 2026; online ahead of print. Link
This guide is general information and is not a substitute for advice about your own situation. Please discuss the benefits and risks of any procedure with your surgeon.
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