When pain needs imaging: X-ray vs MRI vs ultrasound

Most pain does not need a scan

It is natural to want a picture of what is going on, but most muscle, joint and back problems are diagnosed by listening to your story and examining you — and are treated the same way whatever a scan would show. Scans also find plenty of things that are normal for your age: disc bulges, small tendon tears and wear-and-tear changes are common in people with no pain at all, and seeing them on a report can cause worry without changing what helps.

So our clinicians refer for imaging when the result would change treatment, not as a routine step. Typical reasons include a suspected fracture after an injury, nerve symptoms that are persistent or getting worse, a joint that locks or gives way, pain that is not behaving as expected after a reasonable period of treatment, or a need to rule out a specific cause before a procedure. If a scan is needed, we explain why and what we are looking for.

X-ray

An X-ray uses a small dose of radiation to produce an image of bone. It is quick and widely available, and it is the first choice for:

• suspected broken bones after a fall or impact
• joint alignment, and the amount of space in a joint (for example in knee osteoarthritis)
• spinal curves such as scoliosis, and some bone conditions

X-rays do not show muscles, tendons, ligaments, discs or nerves well. An early stress fracture can also be invisible on X-ray, so a normal result does not always rule one out.

MRI

MRI (magnetic resonance imaging) uses a strong magnetic field and radio waves — no radiation — to build detailed images of soft tissue and bone. It is the most useful test for:

• discs and nerves in the spine, for example in persistent sciatica or a suspected disc herniation with worsening nerve symptoms
• ligaments and cartilage in the knee, such as a meniscus tear that locks the joint
• tendons, muscles and bone marrow, including stress fractures that X-ray has missed
• the labrum and cartilage of the hip and shoulder

An MRI scan takes around 20–40 minutes lying still inside a tunnel-shaped scanner, which some people find noisy or confined. It is not suitable for everyone — for example some people with pacemakers or metal implants — and your clinician will check this before referring. Sometimes "MRI with contrast" is requested, where a dye is injected to show certain structures more clearly, for example after surgery or when infection or other specific causes need to be ruled out.

Ultrasound

Diagnostic ultrasound uses sound waves to produce a live, moving image of tissue near the surface. It is radiation-free, quick and well suited to:

• tendons, particularly in the shoulder (for example rotator cuff tendinopathy or a suspected tear), elbow, Achilles and plantar fascia
• fluid, swelling and bursitis
• some nerve problems near the surface, such as carpal tunnel syndrome
• guiding an injection to the right spot

Ultrasound depends heavily on the skill of the person performing it and cannot see deep structures or the inside of bone, so it is not used for the spine or for most joint cartilage. This is a different thing from the therapeutic ultrasound sometimes used in treatment.

Which one, and when?

A rough guide:

• Is a bone broken? X-ray (MRI if the X-ray is normal but suspicion remains)
• Is a disc pressing on a nerve? MRI
• Is a shoulder tendon torn? Ultrasound or MRI
• Is the knee cartilage damaged? MRI
• How much arthritis is there? X-ray
• Is there fluid or bursitis? Ultrasound

Your clinician chooses the test that answers the question that matters for your treatment; sometimes that is no test at all.

How we arrange imaging

Our physiotherapists and chiropractor can refer directly for X-ray, MRI and MRI with contrast through our partner imaging centre, often with same- or next-day appointments, subject to availability. You do not need to go through your GP first. The report comes back to your clinician, who goes through it with you at your follow-up and explains what the findings mean for your plan — including which findings are normal for your age and can safely be ignored. Where diagnostic ultrasound is the more useful test, we will say so and help you arrange it. Where a medical opinion or prescription is needed, we can also arrange an online private GP consultation. We will explain any imaging costs before you book; see our X-ray and MRI referral page and fees page, and if you plan to claim on insurance, check with your insurer and with us before you book.

When imaging is urgent

• Call us for a same-day assessment if you have had an injury and suspect a fracture, if nerve symptoms such as numbness or weakness are getting worse, or if you have a sudden severe flare-up that needs assessing today. We will see you the same day where we can and arrange fast-track imaging where needed.
• Go straight to A&E for more severe symptoms, such as a suspected broken bone with obvious deformity, a deep wound, a head injury or pain so severe that it cannot wait.
• Call 999 for life-threatening signs: loss of bladder or bowel control, numbness around the groin or buttocks, chest pain, a sudden severe headache, or rapidly worsening weakness in your arms or legs.

When to book

If you are wondering whether your pain needs a scan, the most useful first step is an initial assessment at our Bloomsbury clinic. We will examine you, tell you honestly whether imaging would change anything, and arrange it quickly if it would.