What is Ankylosing Spondylitis?
Ankylosing spondylitis (AS) is a type of inflammatory arthritis that primarily affects the spine and the sacroiliac joints (where the spine meets the pelvis). Over time, inflammation can cause the vertebrae in the spine to fuse together, leading to a rigid, inflexible spine — a process called ankylosis. AS is part of a broader group of conditions called spondyloarthropathies.
AS most commonly develops in teenagers and young adults in their 20s and 30s. It is more common in men than women, though women tend to experience milder symptoms. There is a strong genetic association — most people with AS carry the HLA-B27 gene.
Symptoms
- Chronic lower back pain and stiffness — especially in the morning
- Symptoms improve with exercise and worsen with rest
- Neck pain and stiffness
- Fatigue
- Inflammation in other joints (hips, shoulders, knees)
- Enthesitis — pain and tenderness where tendons and ligaments attach to bone
- Eye inflammation (uveitis) — causing red, painful eyes
- Difficulty breathing deeply (in advanced cases, if the rib cage is affected)
Treatment
- NSAIDs — the first-line treatment for pain and stiffness
- Physiotherapy and regular exercise — essential for maintaining flexibility
- Biologics — TNF inhibitors or IL-17 inhibitors for moderate to severe AS
- Posture training and hydrotherapy
Why GPs still miss inflammatory back pain
Most back pain in UK primary care is mechanical. AS (now often called axial spondyloarthritis) is the exception that improves with movement and worsens with rest. Pain that wakes you in the second half of the night, stiffness lasting more than 30 minutes, buttock pain that swaps sides, and a start before age 45 are the clues NICE NG65 asks clinicians to look for. People often spend years being told to 'keep stretching' without an HLA-B27 test, CRP, or rheumatology referral.
More than the spine
AS can inflame the eyes (uveitis — a red, painful, light-sensitive eye that needs same-day ophthalmology), the heels and Achilles insertions, and sometimes the gut or skin. Chest wall involvement makes a deep breath feel tight. These extra-spinal features are why a 'bad back' story plus a red eye should not be treated as two unrelated problems.
What good UK care looks like
NASS and rheumatology teams treat daily spinal mobility work as medicine, not an optional extra. NSAIDs are often taken regularly rather than as required. If inflammation stays active, NHS pathways include TNF or IL-17 inhibitors. Physiotherapy, hydrotherapy and a smoking-cessation conversation (smoking worsens AS) sit alongside drugs. This library page is the overview; the condition subpages cover treatment, diet and exercises in more depth.