Quick answer: An MRI uses magnets and radio waves, not radiation, to show soft tissues and early inflammation. It is important for diagnosing axial spondyloarthritis and can help in rheumatoid arthritis, but NICE says osteoarthritis is usually diagnosed without imaging. Many MRI findings, such as degenerative changes and meniscal tears, are common with age and may not explain your pain.
Checked on 10 October 2026 against the NHS guide to MRI scans, NICE guidelines on osteoarthritis (NG226), spondyloarthritis (NG65), rheumatoid arthritis (NG100) and low back pain (NG59), and published research on findings in people without symptoms.
Many people with joint pain expect an MRI scan to show exactly what is wrong. Sometimes it does. But for many types of arthritis, especially osteoarthritis, an MRI is not needed and can even cause confusion. This guide explains what an MRI is, when it helps with arthritis, what happens on the day, what the report might say and how to make sense of it.
What is an MRI scan?
MRI stands for magnetic resonance imaging. The NHS explains that an MRI scan uses a strong magnetic field and radio waves to take detailed pictures of the inside of your body. It does not use X-ray radiation.
MRI is especially good at showing soft tissues that X-rays cannot, such as:
- cartilage, ligaments, tendons and the meniscus in the knee
- inflammation in the joint lining (synovitis) and in the bone (bone marrow oedema)
- the spinal cord, nerves and discs
- early changes in the bones of the spine and pelvis in axial spondyloarthritis
When is an MRI useful for arthritis?
Osteoarthritis: usually not needed
NICE says osteoarthritis should be diagnosed clinically, without imaging, in people who are 45 or over, have activity-related joint pain and have no morning stiffness or stiffness lasting no longer than 30 minutes. It advises against routine imaging to diagnose osteoarthritis unless there are atypical features or something suggests another diagnosis. It also says imaging should not be used routinely for follow-up or to guide non-surgical treatment.
NICE gives examples of atypical features, including recent injury, prolonged morning stiffness, rapid worsening or deformity, a hot swollen joint, or concerns about infection or cancer. In these situations, a scan may be appropriate.
Suspected axial spondyloarthritis
This is where MRI is most important in rheumatology. NICE recommends that if an X-ray of the pelvis does not show clear changes, or an X-ray is not appropriate, the specialist should request an MRI using an inflammatory back pain protocol. This looks at the whole spine and the sacroiliac joints for signs of inflammation. If the diagnosis cannot be confirmed but suspicion remains high, NICE says a follow-up MRI can be considered.
Rheumatoid and psoriatic arthritis
The NHS says MRI scans may be used to help diagnose and monitor rheumatoid arthritis, alongside X-rays. MRI can show inflammation and early damage before it is visible on X-ray. In practice, many rheumatology teams use ultrasound, which is quicker and can be done in clinic, and use MRI for specific questions.
Low back pain
NICE advises against routine imaging for low back pain in non-specialist settings. In specialist settings, it says imaging should only be considered if the result is likely to change management. An MRI is needed urgently if there are signs of serious problems such as cauda equina syndrome (see below).
Before surgery or for unexplained symptoms
Surgeons may request an MRI to plan certain operations, to look for a mechanical problem such as a locked knee, or when symptoms do not fit the expected pattern.
Why "abnormal" MRI findings are often normal
MRI is very sensitive. It shows many changes that are common with age and do not cause pain. Two well-known studies illustrate this:
- A study of knee MRI in middle-aged and older adults in the New England Journal of Medicine (Englund and colleagues, 2008) found that incidental meniscal findings were common in the general population and became more common with age, including in people with no knee symptoms.
- A systematic review of spine imaging (Brinjikji and colleagues, 2015) found that signs of spinal degeneration were present in high proportions of people without back pain, increasing with age. The authors concluded that many of these features are likely part of normal ageing and should be interpreted alongside the person's symptoms.
This is why your clinician focuses on your symptoms and examination, not just the scan. A report mentioning "degenerative change", a "meniscal tear" or "disc bulge" does not automatically mean that is the cause of your pain, or that you need surgery.
Preparing for an MRI
The hospital will tell you if there is anything you need to do. The NHS says you may be asked to:
- avoid wearing anything with metal, such as jewellery, a bra with wires, hair clips or hearing aids
- remove coins and keys from your pockets
- change into a gown if your clothes have metal parts
- not wear make-up
You will fill in a safety form asking whether you are or might be pregnant, are breastfeeding, have had surgery, have kidney problems, have any metal in your body (such as surgical clips, a pacemaker or dental work) or have allergies, including to contrast dye. Tell the team about any implants, including joint replacements, so they can check the scan is safe and whether metal might affect the pictures.
If you feel claustrophobic
The NHS advises speaking to the hospital before your appointment if you are anxious or have a fear of small spaces. You may be able to have a medicine to help you relax, and you can ask whether someone can be with you. If you have a relaxing medicine, you will need someone to take you home and you should not drive for 24 hours. Some scanners have a wider opening, and for scans of the knee, ankle or wrist your head may be outside the scanner. Ask what to expect.
If lying still is painful
Lying flat and still for a long time can be hard with arthritis. Tell the radiographer in advance. Take your usual pain relief beforehand, ask for pillows or supports, and ask how long the scan will take so you can plan.
What happens during an MRI
The NHS explains that an MRI is carried out by a radiographer and usually takes between 15 minutes and an hour, sometimes longer. You lie on a flat bed that moves into a short tunnel. Depending on the part being scanned, only part of your body may go inside.
- You will be given earplugs or headphones, because the scanner makes loud bangs and clicks.
- The radiographer controls the scanner from another room but can see, hear and talk to you throughout. You will usually be given a buzzer.
- You need to keep still. You may be asked to hold your breath for short periods for some scans.
- For some scans, you may have an injection of contrast dye to show more detail, for example to look for inflammation.
You will not feel the magnetic field or radio waves. Some people feel warm in the area being scanned.
After the scan
You can usually go home straight away and eat and drink as normal. If you had contrast dye, the NHS says you may be asked to wait for up to 30 minutes to check for a reaction. Side effects of contrast are usually mild and short-lived, such as feeling sick, a headache, a metallic taste or dizziness. Allergic reactions are rare. Tell the radiographer if you feel unwell.
Getting your results
The NHS says it usually takes 1 to 2 weeks to get MRI results. A radiologist, a doctor who specialises in imaging, reviews the pictures and writes a report for the clinician who requested it. You may need a follow-up appointment to discuss it. If you have not heard anything after a few weeks, contact the clinician who referred you.
Many people can now see letters or reports in the NHS App or a hospital patient portal. Reading a report on your own can be worrying, because reports use technical language and describe every finding, important or not. Try to wait until you can discuss it with your clinician.
Common terms in MRI reports
| Term | What it usually means |
|---|---|
| Degenerative change | Wear-related changes, very common with age |
| Joint effusion | Extra fluid in the joint |
| Synovitis | Inflammation of the joint lining |
| Bone marrow oedema | Fluid or inflammation in the bone, seen in inflammatory arthritis, injury and osteoarthritis |
| Chondral loss or thinning | Loss of cartilage |
| Osteophytes | Bony spurs, typical of osteoarthritis |
| Erosions | Small areas of bone loss at joint edges, seen in inflammatory arthritis |
| Sacroiliitis | Inflammation of the sacroiliac joints at the base of the spine |
| Meniscal tear | A tear in the knee cartilage pads, common with age and often without symptoms |
MRI compared with other scans
| Test | Best for | Radiation |
|---|---|---|
| X-ray | Bones, joint space, bony spurs, erosions | Small amount |
| Ultrasound | Inflammation in joints and tendons, guiding injections; quick and often done in clinic | None |
| MRI | Soft tissues, early inflammation, spine and sacroiliac joints | None |
| CT | Detailed bone pictures, surgical planning | Higher than X-ray |
See our guide to X-rays for arthritis for more on X-rays, and how arthritis is diagnosed for the bigger picture.
Waiting for an MRI on the NHS
Waits for MRI scans vary. In England, the time you spend waiting for tests usually counts within your 18-week referral-to-treatment period, and many areas now have community diagnostic centres offering scans closer to home. In Scotland, there is a waiting time standard of 6 weeks for key diagnostic tests and investigations. Wales and Northern Ireland have their own targets. If your symptoms change significantly while you wait, tell the clinician who requested the scan. See our waiting list guide for your rights in each nation.
Paying for a private MRI
Some people pay privately for an MRI. Before doing this, check who will interpret the results and act on them. A private scan without a clinician to review it in the context of your symptoms can leave you with a report you do not understand. Some providers require a referral from a doctor or other registered professional. Our guide to private treatment costs explains what to check.
When to get medical help
Do not wait for a planned scan if you have:
- back pain with numbness around your bottom or genitals, new difficulty controlling your bladder or bowels, or weakness in both legs. Go to A&E or call 999, as this could be cauda equina syndrome and needs an urgent MRI
- a hot, swollen, very painful joint with a fever or feeling unwell. Get an urgent GP appointment or contact NHS 111
- a joint that has suddenly given way or locked after an injury and you cannot use it
- wheezing, difficulty breathing or swallowing, or swelling of the face after contrast dye. Tell staff immediately or call 999 if you have left the hospital
Frequently asked questions
Why won't my GP send me for an MRI for knee arthritis?
NICE advises that osteoarthritis can usually be diagnosed from your age, symptoms and examination, and that imaging is not routinely needed unless there are unusual features. Treatment such as exercise and weight management does not depend on a scan.
Can I have an MRI if I have a joint replacement?
Often yes, but tell the team about all implants. They will check that the scan is safe and whether the metal will affect the pictures.
How long does an MRI take?
Usually between 15 minutes and an hour, according to the NHS, depending on the part of the body and how many images are needed.
Is an MRI scan safe?
It does not use radiation, and serious complications are rare. The main risks relate to metal in the body and, rarely, reactions to contrast dye, which is why you complete a safety form.
My MRI report says I have a meniscal tear. Do I need surgery?
Not necessarily. Meniscal tears are common with age, including in people without pain. Your clinician will consider your symptoms, examination and goals before recommending treatment.
How long do MRI results take?
The NHS says usually 1 to 2 weeks. Contact the clinician who referred you if you have not heard after a few weeks.
Can an MRI diagnose rheumatoid arthritis on its own?
No single test can. The NHS explains that rheumatoid arthritis is diagnosed by combining your symptoms, an examination, blood tests and sometimes scans such as X-rays or MRI. A scan showing inflammation supports the diagnosis but does not make it alone.
Will I be told the result on the day?
Usually not. The radiographer takes the pictures but does not interpret them. A radiologist writes the report, which goes to the clinician who asked for the scan.
Sources and further reading
- NHS: MRI scan
- NICE NG226: Osteoarthritis in over 16s
- NICE NG65: Spondyloarthritis in over 16s
- NICE NG59: Low back pain and sciatica in over 16s
- NHS: Rheumatoid arthritis – diagnosis
- Englund M et al. Incidental meniscal findings on knee MRI in middle-aged and elderly persons. N Engl J Med 2008
- Brinjikji W et al. Imaging features of spinal degeneration in asymptomatic populations. AJNR 2015
- NHS inform: NHS Scotland waiting times
- NHS England: Community diagnostic centres
Educational information for people in the United Kingdom, not personal medical, legal or financial advice. NHS processes, rules and prices change, so check the linked official sources and speak to your GP, specialist team or pharmacist about your own situation. Charity no. 1218461. Pending clinical review. If you feel very unwell, call 999 or go to A&E. For urgent advice, contact NHS 111.
Continue with related help
- What happens at a rheumatology appointment — tests you might have
- Arthritis blood tests explained — what results mean
- Questions to ask your consultant — including about scans
- How NHS referrals work — from GP to specialist