Ankylosing spondylitis (AS) is a form of arthritis. It mainly affects the lower back. Other joints and other parts of the body are sometimes affected. Treatment includes regular exercise and anti-inflammatory medicines. The severity of AS varies from mild to severe. It is mild or moderate in most cases. About 8 in 10 people with AS remain fully independent or minimally disabled in the long term and are able to work full-time for the whole of a normal working life. One important point to remember - tell a doctor urgently if you have AS and develop a painful or red eye. An eye complication called uveitis can be serious but can be treated successfully if treatment is given promptly.
Understanding the lower back
The spine is made up of many bones called vertebrae. The vertebrae are roughly circular and between each vertebra is a disc. The discs are made of strong rubber-like tissue which allows the spine to be fairly flexible. Strong ligaments also attach between adjacent vertebrae to give extra support and strength to the spine. There are also various muscles that are attached to the spine which enable the spine to bend and move in various ways. There are also small facet joints that help to attach vertebrae to each other. The sacrum is formed from five fused vertebrae that are joined together. They form a triangular-shaped structure at the bottom of the spine. The two sacroiliac joints are the large long joints that join the sacrum to the main bone of the pelvis (the ilium).
The spinal cord, which contains the nerves that come from the brain, is protected by the spine. Nerves from the spinal cord come out from between the vertebrae to take and receive messages to various parts of the body.
What is ankylosing spondylitis (AS)?
AS is a persistent (chronic) arthritic (rheumatic) disease of unknown cause. It mainly affects the spine and the sacroiliac joints. Sometimes other joints and other parts of the body are affected. The word spondylitis means inflammation of the spine. The word ankylosing means bones that tend to join together (fuse) across a joint.
The lower back is typically the main site of inflammation
In AS, the ligaments of the lower spine become inflamed at the points where they attach to the spinal bones (vertebrae). In time, this can stimulate the bone-making cells and cause some bone to grow and form within the ligaments. In time, these bony growths may become larger and form bony bridges between vertebrae that are next to each other. This may, over time, cause some of the vertebrae in the spine to fuse together with this new abnormal bone material.
The sacroiliac joints and their nearby ligaments also commonly become inflamed. This too may ultimately end in fusion between the sacrum and pelvis. The small facet joints of the spine are also commonly inflamed.
Other areas of the body may be affected
The disease is not always confined to the spine and sacroiliac joints. In some cases, inflammation occurs in other joints and in other parts of the body outside of the spine (detailed below).
Who gets ankylosing spondylitis (AS)?
AS most commonly begins between 20 and 30 years of age, but sometimes first develops in children and older adults. It is three times more common in men than in women. There may be a family history with two or more members of a family being affected. About 1 in 1,000 people in the UK develop AS at some point in their life.
What causes ankylosing spondylitis (AS)?
The cause is not known. However, there is a strong hereditary (genetic) tendency. For example, there is a strong association with a gene called HLA-B27. About 9 in 10 people with AS have this gene compared with less than 1 in 10 in the general population. However, having this gene does not mean that you will automatically get AS. Many people with this gene do not develop AS. Also, some people develop AS who do not have this gene. It is thought that something may trigger AS to develop in people who have an inherited tendency to develop AS, and the gene HLA-B27 provides a strong tendency. As yet, the trigger is not known and other genes and factors may also be involved in causing AS.
What are the symptoms of ankylosing spondylitis (AS)?
The main symptom is back pain. The pain usually starts in the lower back. You may think of it as just mild backache at first. It typically becomes gradually worse over several months. You may have pain over your buttocks, and down the back of your thighs. The buttock pain may be felt sometimes on one side and sometimes on the other side. Coughing or straining may make pain worse. Rest does not make it better. In fact, the pain may wake you from sleep. Instead, exercise and movement usually ease the pain. (This is the opposite to most bouts of common mechanical backache which may alert a doctor to the diagnosis of AS.) The pain tends to be worse first thing in the morning. Lying in bed after waking is often uncomfortable. The pain tends to ease as the day goes on.
The middle (chest part) of the spine may become affected. If this occurs, the joints between the ribs and the spine may also become painful.
Stiffness in the lower spine
The stiffness can be quite severe first thing each morning. It usually improves with activity and exercise, and tends to ease as the day goes on.
Other joint symptoms apart from the spine
Other joints are affected at some stage in about 4 in 10 cases. The most common are the hips, knees, ankles, and shoulders. Affected joints can become painful, stiff, and swollen.
Inflammation of tendons and ligaments
Tendons and ligaments in various parts of the body (in addition to those attached to the bones (vertebrae) of the lower spine) may become inflamed and painful where they attach to bones. Common examples are the Achilles tendon where it attaches to the heel, and where chest muscles attach to the ribs.
Inflammation of part of the eye (uveitis)
Uveitis affects about 1 in 3 people with AS from time to time. Tell a doctor urgently if you have AS and develop a painful or red eye. If you develop uveitis, treatment with eye drops should be started as soon as possible after eye symptoms begin. Treatment of uveitis is usually successful. However, if not treated quickly there can be permanent loss of vision in the eye (partial or complete).
Some people with AS feel generally unwell with symptoms of tiredness or depression. Weight loss or anaemia sometimes occur.
Some other conditions develop more commonly than normal in people who have AS. For example, people with AS have a greater than average chance of developing ulcerative colitis, Crohn's disease, psoriasis, osteoporosis, lung fibrosis, cardiovascular disease (see later) and heart valve problems. Note: most people with AS do not get these conditions - it is just that they are more common in people with AS than would be expected in the general population.
How is ankylosing spondylitis (AS) diagnosed?
This condition is diagnosed from the person's symptoms and X-ray or MRI pictures. Blood tests can be helpful, mainly to rule out other conditions.
As the disease progresses, typical changes develop on X-ray pictures of the sacroiliac joints and spine. The X-ray pictures show the bones (vertebrae) gradually fusing together. However, these changes may take several years to become bad enough to be seen on X-ray pictures.
Until recently, the X-ray changes were the only way to confidently confirm AS. More recently, an MRI scan of the sacroiliac joints has been used to confirm the diagnosis at an earlier stage. An MRI scan can give a much more detailed view of a joint than a traditional X-ray picture and can detect inflammation in the sacroiliac joints.
How does ankylosing spondylitis (AS) progress?
Symptoms can vary in severity and usually wax and wane. Flare-ups of inflammation which cause periods of worse pain and stiffness tend to occur from time to time. If joints outside your spine are affected, they tend to flare up at the same time as back symptoms. The number of flare-ups that occur, how severe they are, and how long they last, can vary greatly from person to person.
In time, the mobility and flexibility of your spine may be reduced. This occurs as the inflammation and bony growths that occur cause gradual joining together (fusion, or ankylosis) of some of your bones (vertebrae). The number of vertebrae involved and the extent of any fusion varies from person to person. A bent-over (stooping) deformity may occur in severe cases.
What are the treatments for ankylosing spondylitis (AS)?
The aims of treatment are:
- To ease pain and stiffness.
- To keep your spine as mobile and flexible as possible.
- To limit the extent of any deformity.
Physiotherapy and exercise
It is vital to have a good posture and a regular exercise routine. This helps you to keep a full range of spinal movement and may help to prevent your spine from stiffening up. Regular specific exercises are thought to limit the extent of any spinal deformity that may develop. The exercises may also ease back pain. You will normally be referred to a physiotherapist who will advise on the exact exercises to do. Exercises should become a routine part of life. Ideally, they should be done daily.
Anti-inflammatory medicines reduce inflammation and ease pain. Their correct name is non-steroidal anti-inflammatory drugs (NSAIDs). An important reason to take these medicines is to ease pain so that you can do regular exercises without much discomfort.
It is thought that anti-inflammatory medicines only ease symptoms but do not alter the course of the disease. Therefore, advice had been to take these medicines as and when the pain flares up. But then if symptoms ease, not to take them. However, a recent research study has suggested that regular long-term use of anti-inflammatory medicines may slow down the progression of AS. Further studies are needed to confirm this.
There are several different anti-inflammatory medicines - for example, ibuprofen, diclofenac and naproxen - but there are many others. If one does not suit, another may be fine. Side-effects sometimes occur with these medicines. For example:
- Stomach pain and bleeding from the stomach are the most serious. The risk of this is higher if you are aged over 65, or have had a duodenal or stomach ulcer. In some situations, your doctor may prescribe another medicine to protect the stomach from these possible problems. Note: stop taking the tablets and see a doctor urgently if you develop any of the following whilst taking anti-inflammatory medicines:
- Stomach (abdominal) pains.
- Passing blood or black stools (faeces)
- Bringing up (vomiting) blood.
- You may not be able to take anti-inflammatory medicines if you have asthma, high blood pressure, chronic kidney disease, or heart failure.
The leaflet which comes with the tablets gives a full list of possible side-effects.
Painkillers such as paracetamol may be sufficient if symptoms are mild between flare-ups. (But note the comment above about the possible benefits of taking long-term anti-inflammatory medicines.) You can also take paracetamol in addition to an anti-inflammatory medicine for top-up pain relief.
Newer powerful medicines have become available in recent years that suppress the immune system. They tend to be divided into two groups: biological therapies and immunomodulators. Immunomodulators are useful in rheumatoid arthritis but research suggests they are not very effective in AS. Biological therapies, however, have made a signficant impact on the treatment of AS.
Biological therapies are genetically engineered proteins such as special antibodies called monoclonal antibodies. They can target specific chemicals of the immune system involved in the inflammation process. In AS, a chemical called cytokine tumour necrosis factor alpha (TNF-alpha) is involved in the inflammation process. Certain medicines in a group called TNF-alpha antagonists (which are really manufactured antibodies) block the action of this chemical and therefore suppress the disease activity.
The TNF-alpha antagonists recommended by the National Institute for Health and Care Excellence (NICE) are etanercept, adalimumab and golimumab. Treatment with one of these medicines is an option in some cases. Etanercept or adalimumab needs to be given by injection every 1-6 weeks depending of the dose and type. Golimumab needs to be injected every month. The medicines require special monitoring, as some people develop serious side-effects. For example, taking these medicines can make you more prone to develop a serious infection. A specialist may advise using one of these medicines if you have moderate or severe AS which has not been helped much by anti-inflammatory medicines.
Regarding TNF-alpha antagonists, the NICE guidelines state:
"Adalimumab and etanercept are recommended as possible treatments for people with severe ankylosing spondylitis who:
- Have active spinal disease as assessed on two occasions 12 weeks apart; and
- Have tried at least two non-steroidal anti-inflammatory drugs (NSAIDs) but they have not worked.
Treatment should be started and supervised by a specialist who is experienced in diagnosing and treating AS. People taking adalimumab or etanercept should have regular check-ups. Treatment should continue only if the person's AS shows an adequate improvement. If the improvement is not maintained or if the medicine stops working then treatment should be stopped. Infliximab is not recommended."
Similar considerations should apply to golimumab.
Occasionally, other medicines are used:
- A steroid injected directly into a badly inflamed joint is sometimes used to ease symptoms.
- Medicines called bisphosphonates are used to treat osteoporosis that is associated with AS.
Other treatments sometimes used include the following:
- Transcutaneous electrical nerve stimulation (TENS) machines are sometimes used to ease pain. (These give tiny electrical currents into the affected area.)
- Heat - for example, a hot shower - may help to ease pain, particularly each morning.
- Some people find regular massage is soothing.
- About 1 in 20 people with AS need a hip replacement at some stage, as their hip sometimes becomes badly affected. Rarely, surgery is needed to correct a severe spinal deformity.
Ankylosing spondylitis (AS) and cardiovascular disease
If you have AS, you have an increased risk of developing cardiovascular disease when you become older. (Cardiovascular disease refers to narrowing of the blood vessels (arteries) by a fatty substance called atheroma. This may eventually lead to conditions such as angina, heart attack or stroke.) It is not clear why the risk is increased in people with AS. It may be that the persistent (chronic) inflammatory nature of the condition is partially responsible. Therefore, you should consider doing what you can to reduce the risk of cardiovascular disease by other means.
For example, if possible:
- Eat a good healthy diet.
- Exercise regularly.
- Lose weight if you are overweight.
- Do not smoke.
- If you have high blood pressure, diabetes, or a high cholesterol level, they should be well controlled on treatment.
What is the outlook (prognosis)?
Although there is no cure for ankylosing spondylitis (AS), the outlook is quite good for most people with the disease. After an initial period of inflammation, in many people with AS the disease settles down to a low level of activity. Flare-ups of symptoms occur from time to time, but are often mild or moderate. In most people with AS, regular exercise and medication keep symptoms away, or much reduced. The lower spine tends to become more stiff and less flexible over the years. In some people, the stiffness is more severe than in others.
About 8 in 10 people with AS remain fully independent or minimally disabled in the long term. This is despite eventual severe restriction of spinal flexibility that occurs in about 4 in 10 people with AS. Most people with AS are able to work full-time for the whole of a normal working life. However, heavy manual work may become difficult. If spinal deformities do arise, they do so after at least 10 years.
About 1 in 10 people with AS have a severe form of the disease, and may become quite disabled over time. However, the recent introduction of treatment with TNF-alpha antagonists (described above) seems to have improved the outlook for people with more severe AS.
In most cases, episodes of arthritis outside the spine and/or eye inflammation do not occur, or only occur now and again. In a small number of cases, these problems outside the spine return (recur) frequently, or become severe. Eye inflammation (uveitis) may lead to blindness if not treated promptly.
People with established AS have an increased risk of fracturing the spine if they are involved in a high-impact accident such as a car crash. This is because the spine becomes more easy to fracture as it becomes more stiff and rigid.
Further help & information
Further reading & references
- Ankylosing spondylitis - adalimumab, etanercept and infliximab; NICE Technology Appraisal Guidance, May 2008
- Golimumab for the treatment of ankylosing spondylitis; NICE Technology Appraisal, August 2011
- El Maghraoui A; Extra-articular manifestations of ankylosing spondylitis: prevalence, Eur J Intern Med. 2011 Dec;22(6):554-60. Epub 2011 Jul 13.
- Braun J, van den Berg R, Baraliakos X, et al; 2010 update of the ASAS/EULAR recommendations for the management of ankylosing Ann Rheum Dis. 2011 Jun;70(6):896-904.
- Dagfinrud H, Kvien TK, Hagen KB; Physiotherapy interventions for ankylosing spondylitis. Cochrane Database Syst Rev. 2008 Jan 23;(1):CD002822.
- Ankylosing spondylitis; NICE CKS, February 2013 (UK access only)
Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. EMIS has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.
Dr Tim Kenny
Dr Nick Imm
Dr Helen Huins