Back Pain Doctor

Sacroiliac Joint, SIJ Ligaments and Lumbopelvic Instability

Pain at the back of the pelvis is one of the most over-explained problems in musculoskeletal medicine. People are told their pelvis is twisted, their joint is out, their core is weak. Very little of that survives contact with the research.

What the research does support is more useful, and more specific. The sacroiliac joint accounts for something like 15 to 30 per cent of axial pain below the L5 level. Pain arises from the ligaments behind the joint roughly as often as from inside it. No scan and no examination finding proves the diagnosis. And the treatment with the most durable evidence is the one that takes months rather than minutes.

This section sets all of that out in full — the anatomy, the diagnostic reasoning, a staged rehabilitation programme with the trial protocols behind it, and an evidence review of every injectable and device that gets offered for this problem, including the trials that found against them.

Get assessed promptly if any of these apply

  • New bladder or bowel disturbance, numbness around the saddle area, or progressive weakness in a leg — this needs same-day assessment.
  • Fever, night sweats, or feeling unwell with the back pain.
  • Unexplained weight loss, or a history of cancer.
  • Significant trauma, or a minor injury in someone with osteoporosis or on long-term steroids.
  • Morning stiffness lasting over 30 minutes, pain that eases with movement and worsens with rest, or night pain waking you in the early hours — particularly if the pain started before age 45. This pattern suggests inflammatory sacroiliitis and needs rheumatology assessment rather than mechanical treatment.

This clinic does not provide emergency or after-hours care. For the first item on that list, go to an emergency department.

The evidence at a glance

Verdicts below follow the 2025 multispecialty consensus guidelines where they cover the treatment, and the primary trials where they do not. Each links to the full review.

Treatment Evidence What that means
Rehabilitation Strongest available The only option with durable randomised evidence. Effects still present two years after treatment in the reference trial — though a 2025 review found most motor control programmes produced no significant short-term pain change.
Prolotherapy Weak evidence Guideline verdict: weak evidence for at least three months of relief. One randomised trial found 58.7 per cent still had at least half their pain relief at 15 months against 10.2 per cent with steroid; a real-world cohort of 103 found 23 per cent reached a clinically important improvement.
PRP Weak, and contested Same guideline verdict as prolotherapy, but the two randomised trials disagree — and the double-blind one found corticosteroid worked better.
Focused shockwave Two small randomised trials Thirty patients against a sham: pain improved, disability did not. Ninety postpartum women against manual therapy: the reverse, and the combined arm did best. Neither went past four weeks. Used alongside the programme.
Corticosteroid injection At least four weeks Guideline verdict, for both intra-articular and extra-articular routes, with the evidence slightly stronger extra-articularly. A short window, not a strategy.
EMTT No studies No published trial at this joint, and no randomised trial in any musculoskeletal condition. Adjunct only, and said so before use.
Radiofrequency ablation Strong — by referral The only 'strong evidence' verdict in the 2025 guidelines: at least six months of relief in extra-articular pain. Not performed here; pain medicine referral.
SIJ fusion Weak or very weak — by referral Large trial effects, but unblinded with self-reported outcomes and manufacturer-employed authors. Guideline verdict is weak or very weak for one year of benefit.

The full section

The joint and its ligaments

Why the ligaments behind the joint matter as much as the joint itself — and why that changes where a needle goes.

Lumbopelvic instability

A useful clinical model that has been badly oversold. Here is the part that holds up.

Getting the diagnosis right

No single test proves it. Here is what each one is actually worth.

The rehabilitation programme

Twenty weeks, four phases, with the criteria for moving between them — and the reason unsupervised versions of this fail.

Protocols for clinicians

Written for referrers and physiotherapists: the parameters, the outcome measures and the effect sizes, without the patient framing.

PRP at the sacroiliac joint

Two randomised trials, opposite conclusions, and the better-designed one is the negative one.

Prolotherapy at the sacroiliac joint

The longest trial record at this joint — and a real-world cohort where fewer than a quarter of patients improved.

Shockwave and EMTT

Two small randomised trials, one sham-controlled, and a device with no trials at all.

Referral, ablation and surgery

The procedures not done here, what their evidence actually shows, and when a referral is the right answer.

What is and is not done here

Provided in this clinic

  • Assessment and diagnosis, including screening for the inflammatory and serious causes.
  • A staged rehabilitation plan, supervised and progressed.
  • Ultrasound-guided intra-articular sacroiliac injection.
  • Ultrasound-guided PRP and dextrose prolotherapy to the posterior sacroiliac ligaments — the structures ultrasound reaches best, and the ones the guidelines find painful about as often as the joint itself.
  • Focused shockwave over the joint line, and radial shockwave for contributing muscular pain.
  • EMTT as an adjunct, with its evidence gap stated first.
  • Referral, with the groundwork done, where a specialist procedure is the right next step.

Referred elsewhere

  • Controlled diagnostic blocks and sacral lateral branch blocks.
  • Sacral lateral branch radiofrequency ablation.
  • Minimally invasive sacroiliac joint fusion.
  • Rheumatology assessment for suspected inflammatory sacroiliitis.
  • Emergency and after-hours care.

Read the referral page for what those procedures involve and what their evidence shows — including the one with the strongest evidence in this whole condition.

Common questions about sacroiliac joint pain

How common is sacroiliac joint pain?
The 2025 multispecialty consensus guidelines put it at 15 to 30 per cent of people whose axial pain sits predominantly below the L5 level. Systematic reviews using controlled diagnostic blocks report 10 to 38 per cent depending on the population and the blocking protocol. Common enough to look for deliberately, and uncommon enough that assuming it is the cause of any buttock pain will usually be wrong.
Can a scan or an examination prove my sacroiliac joint is the problem?
Neither can prove it. The 2025 guidelines describe the evidence for imaging in this condition as unclear or negative, and found that a battery of physical examination tests has reasonable sensitivity but lower specificity — with negative tests carrying more predictive value than positive ones. The closest available reference standard is an image-guided local anaesthetic block, and even a single uncontrolled block has a reported false-positive rate of 20 to 54 per cent.
Is my sacroiliac joint out of alignment?
Almost certainly not in the sense that phrase implies. A systematic review and meta-analysis of 15 palpatory sacroiliac mobility tests across 28 studies found agreement between examiners ranging from no better than chance to moderate at best, and not one study verified that these tests measure joint position at all. The pain is real; that particular explanation is not supported.
What is the best treatment for sacroiliac joint pain?
Rehabilitation, delivered properly — supervised, individualised, progressive and sustained over months rather than weeks. It is the only option here with durable randomised evidence. Injections and devices are considered where a well-delivered programme has not been enough, and each is described on its own page with the evidence for and against it.
Do the SIJ ligaments matter as much as the joint?
Roughly as much. The 2025 consensus guidelines found the prevalence of intra-articular and extra-articular pathology to be comparable, and concluded that an injection into the joint has diagnostic validity for intra-articular pain but not for pain from the surrounding structures. Practically, that means an injection into the joint that does not help has ruled out half the complex, not all of it.
Which sacroiliac treatments are offered at this clinic?
Rehabilitation planning and supervision, ultrasound-guided intra-articular sacroiliac injection, ultrasound-guided PRP and prolotherapy to the posterior ligaments, focused shockwave, and EMTT as an adjunct. Diagnostic and lateral branch blocks, radiofrequency ablation and sacroiliac fusion are not performed here and are arranged by referral. Ultrasound is well suited to the posterior ligamentous structures; it does not on its own confirm placement inside the joint cavity, which is why a formal diagnostic block before ablation or surgery is a referral. Where an injection is warranted but the target cannot be reached safely or reliably under ultrasound, it is referred to a radiologist to perform under CT guidance.

The reference used throughout this section

Consensus practice guidelines on sacroiliac joint complex pain (McCormick & Cohen et al, Pain Medicine 2025;26(12):817-917) ↗

Multispecialty international working group convened by the American Academy of Pain Medicine and ASRA. Twenty-one questions, complete committee consensus on all of them, 21 endorsing organisations. This is the reference point for almost everything in this section.

Last reviewed 2026-09-04. General information about a condition and its treatments, not personal medical advice.

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Your assessment focuses on understanding the likely source of your pain and the most appropriate non-surgical options for your diagnosis, with the aim of reducing pain and improving function.

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