Ankylosing spondylitis is a chronic (long-term) condition that causes inflammation of your spine and other joints. Symptoms include joint pain, stiffness and swelling. It's a form of arthritis, but unlike osteoarthritis or spondylosis, which are caused by wear and tear as we age, ankylosing spondylitis usually first develops in teenagers and young adults. It affects about one in 1,000 people in the UK and can run in families.
Ankylosing means fusing together, while spondylitis refers to inflammation of the spine. In ankylosing spondylitis, your back, neck, hips or knees may slowly become less flexible. In severe cases, inflammation of the ligaments attached to the lower bones of your back can cause bone-making cells to produce bone inside these ligaments. This causes the bones in your lower back to fuse together and can eventually cause these bones to fuse with your pelvis. Ankylosing spondylitis can sometimes affect other joints and areas of the body, including your hips, knees, ankles, shoulders, heels and ribs.
Ankylosing spondylitis mainly affects the spine. Your spine is made of a series of bones stacked on top of each other (vertebrae). In between each vertebra are rubber-like cushions called intervertebral discs, which allow your spine to be flexible. Ligaments connect your spinal bones to each other to make your spine strong.
The bottom of your spine has five vertebrae that are naturally fused together to form a triangular-shaped bone called the sacrum. The sacrum forms part of two large joints which connect it to the pelvis, specifically to a bone in the pelvis called the ilium. These two large joints are called sacroiliac joints.
The most common symptoms are pain and stiffness in your lower back and buttocks, which usually develop between ages 20–30. You might also notice pain or swelling in your joints, including your knees and hips — this occurs in 4 out of 10 people with ankylosing spondylitis.
Other symptoms can include:
You may also unintentionally lose weight. You may find that your symptoms improve with exercise but are worse:
Symptoms usually develop gradually over months or years and can come and go. For some people, symptoms worsen over time, while for others symptoms improve.
See your GP if you have pain, stiffness or swelling in your joints that:
Your GP may refer you to a rheumatologist (specialist in muscles and joints).
Getting an accurate diagnosis for ankylosing spondylitis can take time as it can develop slowly and there’s no single test for it. Your doctor will assess your symptoms and may arrange further investigations to check for inflammation of your spine and joints, such as:
They may also carry out a blood test to detect a specific gene that most people with ankylosing spondylitis carry. However, this test is not completely reliable as some people with ankylosing spondylitis do not carry this gene, while others who do carry this gene may not develop ankylosing spondylitis.
It can take years to confirm a diagnosis of ankylosing spondylitis. This is because X-ray and MRI scans cannot always detect inflammation and fusing of your spine in the early stages of the condition.
A diagnosis can usually be confirmed when an X-ray or MRI scan shows inflammation of your sacroiliac joints (sacroiliitis) and you have one or more of the below symptoms:
If you have all of the above symptoms but sacroiliitis cannot be detected, or you do not have any of these symptoms but sacroiliitis is detected, your doctor will give you a diagnosis of probable ankylosing spondylitis.
The cause of ankylosing spondylitis isn't known, but these factors may increase your risk:
In the general population, about eight in every 100 people have the HLA-B27 gene but the majority will not develop ankylosing spondylitis.
Ankylosing spondylitis can run in families and the HLA-B27 gene is a risk factor for the condition. If you carry this gene and have ankylosing spondylitis, there is a one in two chance that the gene will be passed onto your children. For children carrying this gene, 5–20% will develop the condition.
Ankylosing spondylitis cannot be cured and the damage caused cannot be reversed. However, there are treatments that can make a difference by easing your pain and stiffness, keeping your spine as flexible as possible, and slowing down the progression of the condition.
Regular exercise and physiotherapy are important to improve your posture and the mobility of your spine — this will help prevent your spine from becoming more stiff and painful. Physiotherapy can involve group or individual exercise programs, massage and hydrotherapy. Playing sport and swimming can ease your symptoms too.
Medicines can also help treat flare-ups, including:
Anti-TNF injections and secukinumab are biological medicines as they are not manufactured artificially but are made by living organisms.
The long-term effects of anti-TNF injections are currently unknown, which is why you will need to be carefully monitored if you have these injections. Side effects include becoming more likely to develop a serious infection, such as pneumonia, sepsis or tuberculosis. In very rare cases your risk of developing certain cancers, such as leukaemia and lymphoma, may increase.
Your doctor will usually prescribe anti-TNF injections for 12 weeks, after which they will review your condition. Only if this treatment has shown significant improvement in your condition will your doctor recommend you continue with it.
Other treatments for ankylosing spondylitis depend on the severity of the condition and the affected joints, and might include:
Whichever treatment your doctor recommends, you will need regular check-ups to see how your condition is progressing and if the treatment is working.
For some people with ankylosing spondylitis, their condition improves over time, while for others it worsens. The severity of the symptoms also varies considerably from one person to the next. Some people can remain independent or have minor disabilities, while others become severely disabled due to joint damage and their spine fusing, which causes reduced mobility.
Life expectancy is not affected by the condition but ankylosing spondylitis can increase your risk of developing other life-threatening diseases, such as:
Ankylosing spondylitis can also increase your risk of developing other conditions that can affect your quality of life, including:
What is the main cause of ankylosing spondylitis?
The cause of ankylosing spondylitis isn't known, but there are factors that can increase your risk of developing it. It usually first develops in your late teens or early 20s and is three times more likely to affect men than women. It runs in families and there is a genetic risk factor — more than 9 in 10 people with ankylosing spondylitis carry a gene called HLA-B27. However, you can carry this gene and not develop the condition.
Is ankylosing spondylitis an autoimmune disease?
Yes, ankylosing spondylitis is an autoimmune disease — this refers to diseases where your body attacks its own healthy tissues. Ankylosing spondylitis is also an inflammatory disease as it causes inflammation of the spine and sometimes other joints in your body.
What does ankylosing spondylitis pain feel like?
Ankylosing spondylitis causes dull pain in and around your lower back and buttocks, as well as stiffness. Pain and stiffness can also occur in other joints in your body. Exercise improves the pain while rest either makes no difference or makes the pain worse.
What organs does ankylosing spondylitis affect?
Ankylosing spondylitis mainly affects the spine but can sometimes affect other joints in the body, such as your hips, knees, ankles, shoulders, heels and ribs. It can also increase your risk of developing other conditions that can affect your organs, such as your eyes, lungs, heart, kidneys and liver.
What foods to avoid with ankylosing spondylitis?
There is no dietary cure for ankylosing spondylitis but certain foods can worsen your inflammation and are best to avoid. These include foods:
High in sugar, such as sweets, fruit juices and sauces
High in salt and sodium, such as smoked, cured, preserved or tinned meat, and frozen ready-meals
High in saturated fat, such as cheese, full-fat dairy products, pizza, processed foods and red meat
High in omega-6 fatty acids, such as mayonnaise, pastries, processed foods, salad dressings and vegetable oils
What aggravates ankylosing spondylitis?
A lack of physical activity can aggravate your symptoms but doing too much can also strain your joints. It is important to strike a balance with your physical activity and know when to take a break. Poor posture can also worsen your symptoms by weakening your back muscles. Other factors that can aggravate ankylosing spondylitis include:
Lack of sleep
Not taking your medication as prescribed, eg skipping doses