Ankylosing spondylitis

Ankylosing spondylitis (AS) is a long-term condition in which the spine and other parts of the body become inflamed. It is a type of axial spondyloarthritis and tends to appear first in teenagers and young adults, usually between the ages of 18 and 40 (NHS). When the changes in the spine show on an X-ray, doctors call it AS. When they don’t, but can sometimes be seen on MRI, it is called non-radiographic axial spondyloarthritis. Symptoms and treatment are similar (NHS).

How is ankylosing spondylitis different from desk back pain?

Back pain is very rarely a sign of something serious, and it usually improves within a few weeks, even if it can last longer or come back (NHS). When no clear cause can be found, it is called non-specific back pain. Inflammatory back pain behaves differently. The NHS describes the back pain of AS like this (NHS):

• it gets better with exercise, but not with rest, and may get worse with rest
• pain and stiffness are worse in the morning and at night, and may wake you regularly
• there is often pain around the buttocks

AS can also cause inflammation in other joints such as the hips and knees, and where tendons attach to bone, for example behind or under the heel and where the ribs meet the breastbone. Rib involvement can make it hard to take a deep breath. Fatigue is common, and some people also have eye inflammation (iritis), psoriasis or inflammatory bowel disease.

For a desk worker, the useful question is simple: does your back feel worst after long, still spells and loosen up once you move? If that pattern began before your mid-forties and has lasted for months, it is worth raising with a GP.

Why is ankylosing spondylitis often missed?

NICE warns that axial spondyloarthritis is often misdiagnosed as mechanical low back pain, which delays effective treatment. It affects a similar number of women as men, can occur in people without the HLA-B27 gene variant, and may be present when a plain X-ray looks normal (NICE).

The delay is long. A meta-analysis of 64 studies put the average time from first symptoms to diagnosis at 6.7 years, with no sign of improvement over time. Starting young and having no symptoms outside the spine were among the factors linked with longer delays (Zhao et al., 2021).

NICE advises GPs to refer someone to a rheumatologist when back pain started before 45, has lasted more than three months and comes with at least four further features, such as waking in the second half of the night, buttock pain, improvement with movement, a close relative with spondyloarthritis, or past psoriasis (NICE). The full checklist is explained in Why does my back hurt in the morning?

What helps, and what does the evidence say?

There is no cure, but treatment relieves symptoms and can help delay progression. It usually combines exercise, physiotherapy and medicines, including biological drugs such as anti-TNF treatment (NHS). NICE recommends referral to a specialist physiotherapist for a structured, individual programme with stretching, strengthening and postural work, deep breathing, aerobic exercise and spinal extension through the neck, upper back and lower back (NICE).

A Cochrane review of 14 trials with 1,579 people found that, compared with no exercise, programmes probably slightly improve function and may reduce pain, by about two points on a ten-point scale at the end of the programme. Compared with usual care, they made little or no difference. Most trials were at unclear or high risk of bias, most participants were also on medication, and the effects on spinal mobility and on harms remain uncertain (Regnaux et al., 2019).

When to see a doctor

• Persistent symptoms that fit the pattern above: see a GP, who can refer you to a rheumatologist (NHS).
• A painful red eye, sensitivity to light or blurred vision: NICE advises same-day assessment by an eye specialist (NICE).
• New back pain after a fall or minor injury if you have AS: AS can lead to osteoporosis and spinal fractures (NHS), so get it checked promptly. See vertebral fracture.
• Numbness around your bottom or genitals, changes in bladder or bowel control, or weakness in both legs: call 999 or go to A&E (NHS). More warning signs are listed under red flags.

If your pain looks more like the ordinary kind, lower back pain from sitting covers the common causes.