Sacroiliac joint pain is an under-recognised cause of buttock or groin pain. Treatment usually starts with exercise therapy and activity modification. But not every case settles with simple measures, so an SI joint injection is sometimes needed. When and how is a sacroiliac joint injection performed?
This is part of our wider deep buttock pain guide, which covers every cause of gluteal pain.
What is the sacroiliac joint?
The sacroiliac joints sit between the sacrum (below the lumbar spine) and the pelvic bones. They provide shock absorption and transfer load from the lower body to the upper body.
The sacroiliac joints sit between the sacrum (below the lumbar spine) and the pelvic bones. They provide shock absorption and transfer load from the lower body to the upper body.
Causes of sacroiliac joint pain
Repetitive force on the joint — such as from running — is a common trigger. Others include a direct fall onto the sacroiliac joint, an autoimmune disorder that attacks the joint (sacroiliitis), or pregnancy.
How do we diagnose sacroiliac joint pain?
Diagnosis is challenging. Symptoms overlap with a herniated disc or hip arthritis, the special tests aren’t definitive, and imaging is often normal despite real SI joint pain.
MRI helps exclude sacroiliitis and can rule out lumbar spine pain (sciatica) or hamstring-origin tendinopathy. Some experts regard an image-guided sacroiliac joint injection as the most reliable test: a 75% drop in pain after the injection points strongly to the joint as the source.
Treatment, including a sacroiliac joint injection
We recommend simple treatments first. Physiotherapy strengthens muscles, improves mobility, and addresses soft-tissue problems. A support brace helps, particularly in pregnancy, and anti-inflammatory tablets such as ibuprofen can ease pain. If the pain persists, we consider an SI joint injection. We rarely, if ever, consider surgery.
More about the sacroiliac joint injection
A cortisone injection treats inflammation and pain in the joint. The SI joint is deep and narrow, so accurate imaging is essential to place the cortisone correctly.
More recently, we’ve used platelet-rich plasma (PRP) for selected cases — people with hypermobility or a history of trauma can develop SI joint dysfunction, and may benefit from 1–2 PRP injections to help heal the ligaments and joint. We direct these into the joint and its ligaments.
Traditionally, an SI joint injection used X-ray with dye. Nowadays, many doctors use ultrasound, which avoids radiation exposure and is less expensive. Recent evidence shows similar accuracy: one 2014 randomised study comparing ultrasound with X-ray found ultrasound to be slightly less accurate (89% vs 94%), but patient outcomes were the same in both groups. Sometimes we combine the SI joint injection with a piriformis injection when there are mixed joint and muscle signs.
Sacroiliac joint injection cost
Cost depends on how the injection is done. X-ray-guided injections are expensive — they need a hospital room, nursing staff, and X-ray equipment. Ultrasound-guided injections are usually much cheaper, performed in a clean clinic room without costly extra equipment, and with comparable accuracy. Dr Masci performs ultrasound-guided SI joint injections; please review the current fees here, with Chelsea being the most cost-effective clinic.
Frequently asked questions about a sacroiliac joint injection
Is sacroiliac joint pain common in pregnancy?
Yes. SI joint pain is more common during and after pregnancy, likely from hormonal changes. Treatment follows the same principles — rehab, with or without an injection.
Do I need an X-ray or MRI before an SI joint injection?
Generally yes. SI joint-area pain can come from lumbar nerve compression or pelvic problems such as endometriosis or ovarian cysts, so we recommend an MRI to exclude other sources first.
Why are sacroiliac joint injections so expensive?
It depends on the technique. X-ray-guided injections carry hospital, nursing, and equipment costs. Ultrasound-guided injections cost significantly less for comparable accuracy.
I’ve been told SI joint injections should only be done with X-ray, not ultrasound. Is that right?
We don’t believe so. Ultrasound-guided SI joint injections are safe, accurate, and less expensive — with no radiation exposure.
Are you sedated for an SI joint injection?
Generally, no, with ultrasound guidance. We use a local anaesthetic to numb the area before injecting cortisone or PRP.
Do SI joint injections cause weight gain?
While cortisone has side effects, intermittent injections do not cause weight gain.
How long do SI joint injections last?
It depends on the injectable and the severity. A cortisone injection typically lasts a few months; PRP is expected to last longer. One study showed cortisone for an inflamed SI joint lasted about 6 months.
Psoriatic arthritis vs osteoarthritis of the SI joint — how can you tell?
Both inflammatory arthritis (such as psoriatic or rheumatoid arthritis) and osteoarthritis can affect the SI joint, but their treatments differ. MRI helps — inflammatory arthritis shows inflammation in the middle of the joint with erosions, and rheumatoid arthritis blood tests provide additional information.
Final word from Sport Doctor London about a sacroiliac joint injection
Sacroiliac joint pain is a common, under-reported cause of buttock pain. See a doctor who can diagnose and manage it. Ultrasound-guided SI joint injections are as effective as X-ray-guided injections, at roughly half the price — and we sometimes combine one with a piriformis injection for better results.
Dr Masci performs ultrasound-guided sacroiliac joint injections in London. For costs and booking, contact his team here or call +44 (0) 203 488 0350.
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