What Is Ankylosing Spondylitis?


Ankylosing spondylitis (AS), a type of axial spondyloarthritis, is a chronic condition that causes inflammation of the spinal cord and other areas of the body. The symptoms develop slowly, potentially over several years, and not every patient will experience all of them. AS usually develops between the ages of 18 and 40.

As a response to the inflammation, extra calcium is produced by the body around the different areas of the spine; the cervical spine, the thoracic spine, the lumbar spine, the sacroiliac joint and the coccyx. 

The increase in calcium can make extra pieces of bone grow which can result in areas of the spine fusing together, although this does not occur with all AS patients. 

Experiences of AS differ between patients and there are different factors that might put you more at risk of developing it and various ways to manage the symptoms. 

Causes of ankylosing spondylitis 

Often, there isn’t a distinct, clear reason why some people develop ankylosing spondylitis. There are several factors that can make a person more likely to develop this condition. 


  • There is a strong correlation between the HLA-B27 gene and ankylosing spondylitis. Human leukocyte antigens (HLA) are located on chromosome 6 and their role within the body is to present antigens from viruses and pathogens to cytotoxic T cells; a type of immune cell to help the body distinguish between its own cells and foreign substances.1 The B27 part of the gene is the allele; the version of the gene
  • Possessing the HLA-B27 gene increases the likelihood that AS will develop, but only 2-10% of those carrying the gene will develop the condition2
  • It’s estimated that 8% of the general population have the gene variant, but not all of these people will develop AS3
  • In patients already diagnosed with AS, it’s estimated that between 85-95% of them will test positive for gene4

Being HLA-B27 positive is also associated with other conditions such as inflammatory bowel disease (IBD) and reactive arthritis. 

If you have a parent with AS and the HLA-B27 gene, there’s around a 25% chance of developing the condition.5

Due to the fact that less than 100% of people that possess the HLA-B27 gene variant do develop AS, there must be other causal, environmental factors at play in the development of the condition. 

There are other gene variants that are linked to ankylosing spondylitis but there is not as much research into these as there is for HLA-B27. Some of the other genes that are considered to be implicated in the condition are ERAP1, IL1A, IL23R but there are estimated to be over 60 in total.6


There are several conditions that can increase your risk of developing AS. These include7

  • Crohn’s disease; an inflammatory bowel condition that causes parts of the digestive system to become inflamed
  • Ulcerative colitis; another inflammatory bowel disease that causes inflammation and ulcers to form in the lining of the intestines
  • Psoriasis; a chronic condition affecting the skin, causing flaky, scaly patches of skin to develop

Exactly how the different factors interact to cause Ankylosing Spondylitis is not yet fully understood

Signs and symptoms of ankylosing spondylitis

The signs and symptoms of AS vary from person to person but they usually include:8


  • Pain may be felt in the back, hips, neck and buttocks

 It is usually accompanied by stiffness and is worse during the mornings and evenings. Some patients report the pain waking them up in the night. The pain may lessen during exercise and resting does not alleviate it. 


  • AS can cause inflammation in the joints around your body. Your spine, knees, and wrists are just a few areas that can be affected. 

Tenderness when touching the joint, swelling and warmth of the area around the joint and pain when moving the joint are all signs of arthritis


  • Enthesitis is a painful inflammation in the entheses, the areas where a bone is joined to a tendon or ligament such as at the top of the shin bone.9

Other symptoms

  • Fatigue

Management and treatment for ankylosing spondylitis

Unfortunately, AS is a chronic condition for which there is no cure. However, there are steps to take that can reduce the symptoms of the disease to increase quality of life. You should also have regular follow-ups with your rheumatologist to discuss how you’re coping with the condition. A treatment that works for one person might not be suitable for everyone. 


  • It’s important to keep as active as possible to prevent your spine from becoming stiff. According to the National Axial Spondyloarthritis Society, ‘exercise is the most important thing you can do to help yourself’.  Exercise can slow down the development of the fusion in the spine
  • You might find that swimming or continuing to play sports helps your symptoms; this is a great way to manage your condition. However, it’s still important to get advice from a physiotherapist because they will be able to give you specific exercises to do that will help your spine mobility in the long run.10 Physical therapy offers a range of management options, these could include group exercise workshops and hydrotherapy

The NASS has a huge range of information, guides and even a youtube channel dedicated to informing patients of the best way to exercise with AS and other conditions that fall under the umbrella of axial spondyloarthritis. 


Some patients need to take painkillers such as ibuprofen or paracetamol to manage their condition. 

In cases where a stronger painkiller is needed, these will be prescribed by a doctor who will then be able to monitor your dosage and the effectiveness of the pain relief. 


It’s unusual for AS patients to need surgery but sometimes joints such as the hip will need to be replaced. 

Steroid injections

Corticosteroid injections can be administered directly to inflamed joints. 

Anti-TNF medicine

Tumour necrosis factor (TNF)  is produced by cells causing inflammation in response to injury or infection. Injections of anti-TNF medicine are given to combat the effects of excess inflammation in patients with AS.11

Monoclonal antibody treatments

Monoclonal antibodies are made in a laboratory. They have been used to treat several diseases including cancer. Each antibody is engineered to only bind with one antigen. They can be used as they are, or as delivery vehicles to transport drugs or radioactive substances within the body to the target area.12

In the case of AS, monoclonal antibodies are used as an alternative to anti-TNF medications with the aim of blocking the effects of a proinflammatory protein called interleukin-17(IL-17).13

JAK inhibitors

JAK (Janus Kinase) inhibitors are more recent development in treatment for AS. They also aim to reduce inflammation by blocking pro-inflammatory proteins within the immune system.14

Diagnosis of ankylosing spondylitis

AS is usually diagnosed by a rheumatologist; a doctor that specializes in the health of joints, bones and muscles. Unfortunately, it can take a while to get an accurate diagnosis as the condition is often presumed to be backache or some other common back complaint. 

There isn’t a single test that can give you a clear diagnosis of AS but the following might be carried out:

  • A discussion about your symptoms
  • A discussion about your medical history, including if there is a family history of AS or similar conditions
  • A blood test can help detect inflammation
  • X-rays and MRI scans can look at your spine in more detail
  • A physical examination
  • A blood test can be carried out to see if you possess the HLA-B27 gene

The rheumatologist will aim to join the pieces of the puzzle together to form an accurate diagnosis. 

Risk factors

The risk factors for AS are as follows:

  • Possessing the HLA-B27 gene variant
  • Having a family history of the disease
  • AS is usually diagnosed in younger patients compared to other forms of arthritis
  • Exposure to certain toxins and pollutants. Why this increases the risk is not yet fully understood15
  • Having one of the conditions that sometimes occur alongside AS mentioned earlier in this article, such as inflammatory bowel disease(IBD)


Acute anterior uveitis

Also known as iritis, inflammation of the uvea in the eye can occur as a complication of AS. It causes redness and pain in either one eye or both and must be treated immediately. Treatment is usually with steroid eye drops and drops to dilate the pupil in the eye to prevent further damage. 

Most people fully recover from uveitis but it’s important to get medical attention as soon as possible because irreversible sight damage can occur if treatment isn’t accessed promptly. 

AS is not the only condition that has a relationship with iritis, it’s also associated with autoimmune conditions and can occur after an eye injury.16

Increased risk of fractures

 those who have had AS for a longer period of time, or those whose bones of the spine have fused together in places, might be more likely to experience a fracture in your spine. 

For this reason, you should always let a doctor know that you have AS if you were to be in an accident or suffer a fall.17

Some AS patients also develop osteoporosis which also increases the likelihood of fractures. 

Reduced flexibility

Sometimes, the stiffness caused by the condition can reduce your flexibility and therefore can affect mobility. 

Cardiovascular disease(CVD)

If you have AS, your risk of developing cardiovascular disease, including stroke and heart disease. To reduce the risk, it's important to follow lifestyle advice such as not smoking and regularly exercising. 

In some cases, you may be prescribed medication to lower blood pressure and cholesterol.18

Cauda equina syndrome

Cauda equina syndrome is a rare but serious condition in which the nerves at the bottom of the spine become compressed. 

If left untreated, paralysis can ensue. Therefore immediate medical attention is necessary if you suddenly experience:19

  • Incontinence, either urinary, fecal, or both
  • An inability to urinate
  • Weakness, especially in the legs
  • Numbness or a change in sensation in the legs, buttocks, and thighs
  • Burning or tingling sensations in your legs


How can I prevent ankylosing spondylitis?

At present, there is no known way to prevent AS. 

How common is ankylosing spondylitis?

There are roughly 200,000 people in the UK currently that have been diagnosed with the condition.20 It is more common in people assigned male at birth but this could be a reflection of the fact that many conditions, particularly those causing pain, are under-diagnosed in those people assigned female at birth.

When should I see a doctor?

If you’re concerned that you may have any of the symptoms of AS, or if your family has a history of the disease, you should consider speaking to a doctor.  


Ankylosing spondylitis is a painful condition in which the spine and other areas of the body become inflamed. Symptoms include back pain and stiffness. There are varying treatments that can help to manage the symptoms, but the main way to reduce the symptoms is to take part in the exercise. No single factor that causes the disease, but it's thought that an interplay of genetic and environmental factors occurs. Having a family history of the disease or a specific gene type called HLA-B27 increases the risk of developing AS. Overall, AS is a debilitating condition and the outlook varies from person to person. There is a lot of information available detailing how best to manage your symptoms and ongoing medical support should be offered to all patients. 


  1. Parameswaran P, Lucke M. Hla b27 syndromes. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 [cited 2023 May 30]. Available from: http://www.ncbi.nlm.nih.gov/books/NBK551523/ 
  2. Frank J, MD, Peer-Reviewed R. Ankylosing spondylitis causes and risk factors | arthritis-health [Internet]. [cited 2023 May 30]. Available from: https://www.arthritis-health.com/types/ankylosing-spondylitis/ankylosing-spondylitis-causes-and-risk-factors 
  3. Ankylosing spondylitis - Causes [Internet]. NHS.UK. 2018 [cited 2023 May 30]. Available from: https://www.nhs.uk/conditions/ankylosing-spondylitis/causes/ 
  4. Frank J, MD, Peer-Reviewed R. Ankylosing spondylitis causes and risk factors | arthritis-health [Internet]. [cited 2023 May 30]. Available from: https://www.arthritis-health.com/types/ankylosing-spondylitis/ankylosing-spondylitis-causes-and-risk-factors 
  5. Ankylosing spondylitis: MedlinePlus genetics [Internet]. [cited 2023 May 30]. Available from: https://medlineplus.gov/genetics/condition/ankylosing-spondylitis/ 
  6. Ankylosing spondylitis (AS): symptoms, causes & treatment [Internet]. Cleveland Clinic. [cited 2023 May 30]. Available from: https://my.clevelandclinic.org/health/diseases/16595-ankylosing-spondylitis-as 
  7. Ankylosing spondylitis - Symptoms [Internet]. NHS. UK. 2018 [cited 2023 May 30]. Available from: https://www.nhs.uk/conditions/ankylosing-spondylitis/symptoms/ 
  8. Schett G, Lories RJ, D’Agostino MA, Elewaut D, Kirkham B, Soriano ER, et al. Enthesitis: from pathophysiology to treatment. Nat Rev Rheumatol [Internet]. 2017 Dec [cited 2023 May 30];13(12):731–41. Available from: https://www.nature.com/articles/nrrheum.2017.188 
  9. Ankylosing spondylitis - Treatment [Internet]. NHS. UK. 2017 [cited 2023 May 30]. Available from: https://www.nhs.uk/conditions/ankylosing-spondylitis/treatment/ 
  10. Jang D in, Lee AH, Shin HY, Song HR, Park JH, Kang TB, et al. The role of tumor necrosis factor alpha (Tnf-α) in autoimmune disease and current TNF-α inhibitors in therapeutics. Int J Mol Sci [Internet]. 2021 Mar 8 [cited 2023 May 30];22(5):2719. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7962638/ 
  11. Https://www. Cancer. Gov/publications/dictionaries/cancer-terms/def/monoclonal-antibody [Internet]. 2011 [cited 2023 May 30]. Available from: https://www.cancer.gov/publications/dictionaries/cancer-terms/def/monoclonal-antibody 
  12. Fauny M, Moulin D, D’Amico F, Netter P, Petitpain N, Arnone D, et al. Paradoxical gastrointestinal effects of interleukin-17 blockers. Annals of the Rheumatic Diseases [Internet]. 2020 Sep 1 [cited 2023 May 30];79(9):1132–8. Available from: https://ard.bmj.com/content/79/9/1132 
  13. Feintuch S. Ankylosing spondylitis risk factors: here’s what really causes ankylosing spondylitis [Internet]. CreakyJoints. 2019 [cited 2023 May 30]. Available from: https://creakyjoints.org/about-arthritis/axial-spondyloarthritis/axspa-overview/ankylosing-spondylitis-risk-factors/ 
  14. Uveitis [Internet]. NHS. UK. 2017 [cited 2023 May 30]. Available from: https://www.nhs.uk/conditions/uveitis/ 
  15. Ankylosing spondylitis (AS) [Internet]. Versus Arthritis. [cited 2023 May 30]. Available from: https://www.versusarthritis.org/about-arthritis/conditions/ankylosing-spondylitis/ 
  16. Ankylosing spondylitis - Complications [Internet]. NHS. UK. 2018 [cited 2023 May 30]. Available from: https://www.nhs.uk/conditions/ankylosing-spondylitis/complications/ 
  17. Cauda equina syndrome: symptoms, treatment & causes [Internet]. Cleveland Clinic. [cited 2023 May 30]. Available from: https://my.clevelandclinic.org/health/diseases/22132-cauda-equina-syndrome 
  18. Ankylosing spondylitis [Internet]. [cited 2023 May 30]. Available from: https://www.nhsinform.scot/illnesses-and-conditions/muscle-bone-and-joints/conditions/ankylosing-spondylitis 
This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Jessica Gibson

Bachelor of Science- BSc(Hons)- Health Sciences- The Open University

Jessica is a Health Sciences graduate with a passion for both Science and English and is delighted to have found a way to combine the two. She is a motivated and enthusiastic writer determined to make scientific information more widely accessible.
Jessica is especially interested in infectious diseases, neurodegenerative diseases, the impact of trauma on physical health, health equity and the health of children residing in developing nations.

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