Spondyloarthritis

Overview

Spondyloarthritis is a family of linked inflammatory conditions that share a tendency to affect the spine, the joints where the spine meets the pelvis (the sacroiliac joints), and the points where tendons and ligaments attach to bone. It includes ankylosing spondylitis — the classic form, in which inflammation is centred on the spine — as well as psoriatic arthritis, reactive arthritis, and the arthritis that can accompany inflammatory bowel disease.

Doctors group these conditions together because they behave in similar ways, tend to run in the same families, often share the gene marker HLA-B27, and respond to the same treatments. Spondyloarthritis is broadly divided into an axial form, affecting mainly the spine and pelvis, and a peripheral form, affecting mainly the limbs — though many people have features of both.

It usually begins in late teens or early adulthood, which is younger than most other kinds of arthritis. Recognising it early matters, because starting treatment before lasting stiffness sets in gives the best long-term results, and modern treatment has changed the outlook substantially.

Symptoms

The most characteristic symptom is inflammatory back pain. Unlike ordinary mechanical back pain, it comes on gradually over weeks, tends to affect younger adults, is worse with rest and in the second half of the night, and eases with movement and exercise. Prolonged morning stiffness is typical, and pain is often felt deep in the buttocks, sometimes alternating from side to side.

Beyond the spine, spondyloarthritis can inflame the tendon attachments — most commonly at the heel, causing pain in the back or underside of the foot — and can cause a whole finger or toe to swell (dactylitis). Larger joints such as the hips, knees and shoulders may be involved.

Several features outside the joints point towards spondyloarthritis and help make the diagnosis: a painful red eye from inflammation inside the eye (uveitis), the skin rash of psoriasis, and inflammatory bowel disease. Fatigue is common, particularly when the inflammation is active.

Causes and risk factors

The exact cause is not known, but genetics play a strong part. Many people with axial spondyloarthritis carry the gene marker HLA-B27. Carrying it clearly raises the risk, yet most people who have the marker never develop the condition, so it is a piece of the picture rather than a diagnosis in itself.

A family history of spondyloarthritis, psoriasis, uveitis, or inflammatory bowel disease increases the likelihood, because these conditions share underlying pathways. Spondyloarthritis is not caused by injury, posture, or lifestyle, though staying active strongly influences how well someone does with it over the years.

Diagnosis

Diagnosis rests on the overall pattern — the history of inflammatory back pain or joint symptoms, a physical examination of spinal movement and tender points, blood tests, and imaging. Because the symptoms overlap with the very common problem of ordinary back pain, the diagnosis is often delayed, and a rheumatologist looks specifically for the inflammatory pattern and the associated features.

Imaging is central. Established disease can show characteristic changes in the sacroiliac joints on an X-ray, but these changes take years to appear. An MRI scan can reveal active inflammation much earlier, which allows the condition to be recognised long before permanent change develops. This distinction — between early, non-radiographic disease and later, established disease — guides how the condition is described and treated.

Investigations

Tests usually include inflammation markers (ESR and CRP), which are raised in some but not all people, and the HLA-B27 gene test, which supports the diagnosis when positive in the right setting. X-rays of the pelvis and, increasingly, MRI of the sacroiliac joints and spine are used to look for inflammation and any structural change.

Where relevant, the skin, nails, eyes and bowel are assessed, because the specific type of spondyloarthritis — and therefore some treatment choices — depends on which of these are involved. Tests are also repeated over time to judge how active the disease is and how well treatment is working.

Treatment

Exercise and physiotherapy are the foundation of treatment and are as important as any medicine. A regular programme of stretching, back extension, and aerobic exercise helps maintain posture, flexibility and function, and people who keep this up tend to do markedly better over the long term.

Anti-inflammatory medicines (NSAIDs) are usually the first medicines used and can be very effective at controlling inflammatory back pain. When symptoms remain active despite these, biologic and targeted medicines — which block specific messengers that drive the inflammation, such as TNF and IL-17 — have transformed treatment for axial disease and are highly effective. For peripheral joint disease, conventional disease-modifying medicines such as methotrexate also have a role. The choice is tailored to whether the disease is mainly axial or peripheral and to the associated features such as psoriasis or bowel disease.

Living with spondyloarthritis

Daily exercise is the single most valuable habit. Keeping the spine mobile, maintaining good posture, and doing regular back and breathing exercises protect long-term movement; activities such as swimming are particularly well suited. Not smoking is important, as smoking is linked to worse spinal disease and a poorer response to treatment.

Because the eyes can be involved, a sudden painful red eye should be seen promptly, as uveitis needs quick treatment. Attending regular reviews allows treatment to be stepped up if the disease becomes more active. With early diagnosis and consistent care, most people with spondyloarthritis stay active, keep working, and maintain a good quality of life.