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MRI scans

MRI sacroiliac joints

A scan of the sacroiliac joints that detects the early inflammation of axial spondyloarthritis before X-ray changes appear.

What to expect

  • Preparation: Usually none - eat, drink and take medication as normal unless told otherwise. You will complete a safety questionnaire covering implants and previous surgery, and remove all metal items before the scan.
  • During the test: You lie on a motorised couch that moves into the scanner. The machine is noisy, you wear ear protection, and you need to keep as still as possible. Most MRI examinations take 20-45 minutes.
  • Results: A consultant radiologist reports the scan, typically within 24-72 hours of your appointment.
  • Who follows up: The report goes to your referring GP or specialist, who explains the findings and arranges any follow-up.
  • Cost: an indicative cost varies by provider.

About this test

A scan of the sacroiliac joints that detects the early inflammation of axial spondyloarthritis before X-ray changes appear. It is usually recommended for inflammatory-pattern back pain - morning stiffness, night pain, onset under 45.

How to access it privately

You can arrange a private MRI either with a referral from your GP or specialist or, for many scans, by self-referring as a self-pay patient with a short pre-scan questionnaire. Routine NHS diagnostic waits are often long - frequently measured in months - whereas private slots are typically available within days to around two weeks. Costs vary by provider and should be confirmed with the provider before booking.

Frequently asked

Common questions about MRI sacroiliac joints.

Quick, plain-English answers to what people ask us most.

  • What is a sacroiliac joint MRI and what does it show?

    This scan focuses on the sacroiliac joints, which connect the base of the spine to the pelvis, showing detailed images of the bone and surrounding soft tissue. It's particularly useful for detecting inflammation in these joints.

  • Why would a doctor order this scan?

    It's commonly used to investigate persistent lower back or buttock pain when inflammatory conditions such as ankylosing spondylitis or other forms of spondyloarthritis are suspected. It can pick up early inflammatory changes that x-rays often miss.

  • Do I need to prepare for the scan?

    There's usually no special preparation required for this scan. Mention any metal implants or previous pelvic surgery when booking, as with any MRI.

  • What happens during the scan?

    You lie on your back on the scanner table while the pelvic area is imaged, and the scan typically takes around 20 to 30 minutes. Staying still throughout helps produce the clearest images.

  • Does it hurt, and are there any risks?

    The scan itself is painless, though lying flat can be uncomfortable if your back or pelvic pain is significant. There's no radiation involved.

  • How long do results take?

    A radiologist reviews the images, with private results usually available within a few days. Your rheumatologist or specialist will then explain the findings, often alongside blood tests.

  • What do abnormal results mean?

    Findings might include active inflammation (sacroiliitis) or structural changes suggesting a longer-standing inflammatory process. Your rheumatologist will interpret this alongside your symptoms, examination and blood markers to reach a diagnosis and discuss treatment.

  • How much does a private sacroiliac joint MRI cost, and is it available on the NHS?

    This scan is available on the NHS, typically via a rheumatology referral, though waiting times vary. Privately, scans are usually available within days with specialist reporting; cost varies by provider.

  • Is a sacroiliac joint MRI accurate and reliable?

    MRI is considered the most sensitive imaging test for detecting early inflammatory changes in the sacroiliac joints, often before x-ray changes appear. It's a key part of diagnosing inflammatory back conditions when used alongside clinical assessment and blood tests.

  • How do I book a private sacroiliac joint MRI, and how quickly can I be seen?

    Private imaging providers can typically arrange this scan within a few days, sometimes alongside a rheumatology consultation. Contact a provider directly to check availability.