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Health condition · Clinically reviewed

Ankylosing spondylitis, axial spondyloarthritis — modern MRI diagnosis and biologics.

A chronic inflammatory disease of the spine and sacroiliac joints. Early MRI diagnosis is game-changing; NSAIDs, biologics and posture rehab transform outcomes.

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A radiographer guides a patient onto the bed of an advanced 3 Tesla MRI scanner in a London imaging suite

Why trust this guide

  • 01

    Clinically reviewed

    Written by our editorial team and reviewed by a registered UK clinician before publication.

  • 02

    Sourced from guidance

    Every claim is checked against NICE, ASAS or peer-reviewed sources you can see at the end.

  • 03

    Current for 2026

    Reflects current UK guidance on early MRI diagnosis, biologics and posture-focused rehab.

Key facts

Ankylosing spondylitis at a glance.

The essentials, in plain English — what AS is, how it is diagnosed, and how it is treated in the UK today.

  • Definition

    Axial spondyloarthritis is a chronic inflammatory disease of the spine and sacroiliac joints — ankylosing spondylitis is the radiographic form, once structural change is visible on X-ray.

  • Age of onset

    Symptoms typically begin before age 45 — often in the late teens or twenties, and frequently under-recognised for years.

  • Inflammatory back pain

    The pattern matters: night-time pain, morning stiffness lasting more than 30 minutes, and improvement with movement.

  • MRI is diagnostic

    MRI of the sacroiliac joints shows active inflammation years before X-ray changes — it is the single most important test.

  • HLA-B27

    The HLA-B27 gene is positive in around 90% of people with ankylosing spondylitis — helpful, but not diagnostic on its own.

  • Biologics

    Anti-TNF and IL-17 inhibitors have transformed outcomes for high-activity disease that does not respond to NSAIDs.

Why this guide matters

Early MRI diagnosis is everything.

The years between symptom onset and diagnosis have shortened dramatically thanks to MRI — the earlier the diagnosis, the better the long-term outcome.

  • A window of opportunity

    MRI detects sacroiliac inflammation years before X-ray change — treatment can start before permanent fusion.

  • Modern medicines change lives

    Anti-TNF and IL-17 biologics mean sustained low-activity disease is realistic for most people today.

  • Whole-person care

    Alongside the spine, eyes, bowel, cardiovascular health and mood all deserve active attention.

How the diagnosis is made

From first back pain to a clear plan.

The steps a UK GP and rheumatology team will normally follow, in order — so you know what to expect and why.

  1. 01

    Recognising

    Symptom pattern

    Inflammatory back pain: onset under 45, night pain, morning stiffness over 30 minutes, better with movement.

  2. 02

    Recognising

    Bloods

    CRP for inflammation and HLA-B27 genetic testing — a positive B27 in the right context raises suspicion substantially.

  3. 03

    Recognising

    Sacroiliac MRI

    MRI of the sacroiliac joints detects active inflammation (bone marrow oedema) years before structural change.

  4. 04

    Confirming

    X-ray for radiographic AS

    Plain X-ray of the sacroiliac joints and spine confirms radiographic ankylosing spondylitis when structural change is present.

  5. 05

    Confirming

    BASDAI activity scoring

    The Bath Ankylosing Spondylitis Disease Activity Index quantifies symptoms and guides treatment escalation.

  6. 06

    Baseline

    Eye and bowel screen

    Screen for extra-articular disease — uveitis, inflammatory bowel disease and psoriasis are all associated.

  7. 07

    Baseline

    Rheumatology referral

    NICE recommends specialist referral for suspected axial spondyloarthritis — do not wait for X-ray changes.

Typical timeline: 4–8 weeks from first appointment to a confirmed MRI-based diagnosis.

Symptoms

What ankylosing spondylitis actually feels like.

The pattern is more telling than any single symptom — inflammatory back pain, morning stiffness, enthesitis and the extra-articular features.

  • Inflammatory back pain

    Deep low-back or buttock pain, worse at night and in the early morning, that eases with movement.

  • Morning stiffness

    Prolonged early-morning stiffness lasting over 30 minutes — a hallmark of inflammatory back pain.

  • Uveitis

    A painful red eye with light sensitivity — anterior uveitis affects around a third of people with AS.

  • Enthesitis

    Inflammation where tendons attach to bone — heels, elbows, ribs — often overlooked as ordinary tendonitis.

  • Inflammatory bowel comorbidity

    Crohn’s disease and ulcerative colitis are more common in AS — new bowel symptoms deserve investigation.

  • Psoriasis comorbidity

    Skin and nail psoriasis overlap with spondyloarthritis — flag new plaques to your rheumatologist.

  • Heel pain (enthesitis)

    Achilles or plantar-fascia pain without an injury — a classic enthesitis presentation of AS.

  • Red flag

    An acute painful red eye — treat as uveitis until proven otherwise and seek same-day ophthalmology review.

Treatment

How ankylosing spondylitis is treated in the UK.

A layered approach: continuous NSAIDs and posture-focused exercise first, biologics or JAK inhibitors for active disease — with surgery reserved for advanced hip involvement.

  • NSAIDs continuous

    Regular NSAIDs remain first-line — used continuously in active disease, they reduce symptoms and may slow progression.

  • Physiotherapy and exercise

    The mainstay of long-term care — daily mobility, posture and back-extension work preserves spinal movement.

  • Anti-TNF biologics

    Adalimumab, etanercept and infliximab — highly effective when NSAIDs fail; usually delivered by rheumatology.

  • IL-17 inhibitors

    Secukinumab and ixekizumab target IL-17 signalling — an alternative to anti-TNF for active disease.

  • JAK inhibitors

    Oral small molecules blocking intracellular immune signalling — used when biologics are unsuitable or ineffective.

  • Sulfasalazine

    Useful for peripheral joint involvement, though it does not modify the axial (spinal) disease.

  • Local injections

    Steroid injections into inflamed enthesis, sacroiliac joints or peripheral joints for focal flares.

  • Total hip replacement

    Reserved for advanced hip involvement — modern arthroplasty transforms mobility in the small group who need it.

What this guide is based on

The sources behind every claim on this page.

UK national guidance and specialist society standards, current at the time of last review.

Key references

Guidelines and standards we relied on.

A quiet reminder

This guide is for information, not medical advice.

Your GP or rheumatology team knows your history and can tell you which parts apply to you. If in doubt, get seen.

  • NICE. Spondyloarthritis in over 16s: diagnosis and management (NG65).

  • British Society for Rheumatology. Guidelines library.

  • ASAS. Assessment of SpondyloArthritis International Society recommendations.

  • National Axial Spondyloarthritis Society (NASS). Patient information and support.

Red flags

When ankylosing spondylitis becomes an emergency.

AS is usually a slow, chronic disease — but these situations need same-day medical attention.

  • Acute uveitis

    A painful red eye with blurred vision or light sensitivity — same-day ophthalmology review, do not wait.

  • Cauda equina

    New leg weakness, saddle numbness or bladder or bowel disturbance — a fused spine can fracture and compress nerves; attend A&E.

  • Cervical spine fracture

    Even minor neck trauma in a fused spine can cause serious fracture — treat neck pain after any injury as urgent.

  • IBD flare

    New bloody diarrhoea, weight loss or severe abdominal pain — contact your team; some biologics affect gut disease.

  • Cardiovascular event

    Chest pain or sudden breathlessness — AS increases cardiovascular risk; do not delay assessment.

  • Post-biologic infection

    Fever, night sweats or new cough on a biologic — screen for TB and PJP; contact your rheumatology team.

  • Pregnancy planning

    Some biologics and NSAIDs need adjusting around conception — plan ahead with your rheumatology team.

  • Osteoporosis-related fracture

    Sudden severe back pain in AS may be a vertebral fracture — imaging is essential before assuming a flare.

  • Aortic root involvement

    Rarely, AS affects the aortic valve — new breathlessness or a new murmur needs cardiology review.

Living with it

A long-term condition, but a very manageable one.

Four things that make the biggest difference day to day — movement, a flare plan, nutrition, and regular reviews.

A quiet reminder

Consistency beats intensity, every time.

Small, steady changes — kept up for months — do more than a heroic week that does not last.

  1. 01 Movement

    Exercise is medicine

    Daily mobility, posture and back-extension work is the single most important thing you can do for AS.

  2. 02 Flares

    Have a plan

    Know what steps you take when a flare starts — and when to contact your rheumatology team.

  3. 03 Nutrition

    No magic diet

    A Mediterranean-style diet, healthy weight and not smoking all help; supplements have less evidence.

  4. 04 Reviews

    Regular reviews matter

    BASDAI scoring at intervals guides treatment escalation and drives long-term remission.

Frequently asked

Everything we get asked about ankylosing spondylitis.

Quick answers on diagnosis, MRI, HLA-B27, biologics, IL-17 inhibitors and daily life.

  • What is ankylosing spondylitis?

    Ankylosing spondylitis is a chronic inflammatory disease of the spine and sacroiliac joints. It is the radiographic form of axial spondyloarthritis — over time, untreated inflammation can lead to spinal fusion.

  • How is ankylosing spondylitis diagnosed?

    By pattern (inflammatory back pain under age 45, night pain, morning stiffness over 30 minutes), blood tests (CRP and HLA-B27) and — crucially — MRI of the sacroiliac joints, which detects inflammation years before X-ray changes.

  • What is HLA-B27 and why does it matter?

    HLA-B27 is a genetic marker present in around 90% of people with ankylosing spondylitis. A positive result in the right clinical context raises suspicion, but it is not diagnostic on its own — plenty of B27-positive people never develop AS.

  • Why is MRI so important?

    MRI of the sacroiliac joints shows active bone marrow inflammation years before X-ray changes appear. This has revolutionised diagnosis, allowing treatment to start before permanent spinal fusion develops.

  • What are biologics for AS?

    Anti-TNF (adalimumab, etanercept, infliximab) and IL-17 (secukinumab, ixekizumab) inhibitors are injected antibodies that target inflammatory signalling. They are used for active disease that does not respond to NSAIDs and have transformed outcomes.

  • Can you still exercise with ankylosing spondylitis?

    Not only can you — you should. Daily mobility, posture and back-extension work is the mainstay of long-term care and preserves spinal movement more than any medication.

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