- Ankylosing spondylitis (AS) is a form of arthritis that causes inflammation of the spine.
- It commonly affects the lower back and can affect the functioning of the spine.
- Therapy and some medications, like biologics, can help.
Ankylosing spondylitis (AS) is a form of inflammatory arthritis that most often affects your lower back, causing pain, stiffness, and, in severe cases, fusion (joining together) of the bones in your spine.
The exact cause of AS is unknown. It occurs when the immune system attacks healthy cells in the body. This immune response leads to inflammation.
The inflammation is responsible for the stiff, painful feeling most people with AS feel in their lower back. For this reason, it is known as inflammatory back pain.
This inflammation affects more areas than just a person’s lower back. It can cause joint pain and affect other organs, such as the eyes. It is also associated with other diseases, such as irritable bowel disease, which affects between 5% and 10% of people with AS.
Mechanical back pain is another type of back pain.
This type of pain occurs due to changes in the structure and functioning of the back. You may experience it frequently or rarely, and it can result from everyday tasks like lifting too much weight or poor sleep positions.
Back pain and stiffness are the most common features of AS. But lower back pain and stiffness are not enough for a doctor to recognize and diagnose AS. This often means delays in making the connection between lower back pain and AS.
By contrast, it took an average of 28 days for a rheumatologist to make an AS diagnosis once a person was referred. While not all people with back pain have AS, a person with persistent lower back pain with no other explanation may want to see a specialist.
Other reports are not as favorable. According to one survey, it can take up to 10 years of going to doctors and specialists for a person to receive an AS diagnosis.
Some evidence suggests that time between initial back pain and AS diagnosis is improving.
In a 2020 study, researchers found that between 2007 and 2017, diagnosis rates increased. This means that doctors may be getting better adept at recognizing and diagnosing AS instead of assuming it is mechanical back pain.
Telling the difference between mechanical back pain and inflammatory back pain can be tricky.
According to CreakyJoints, you should ask yourself the following questions to help determine if you have mechanical or inflammatory back pain:
- Does it feel worse when resting or sitting for long periods?
- Did it start before age 40?
- Can it get bad enough to wake you in the middle of night and prevent you from getting additional sleep?
- Does moving and exercise generally make the pain feel better?
- Will pain improve when taking a nonsteroidal anti-inflammatory drug (NSAID), like ibuprofen?
- Do other symptoms occur with the back pain, such as inflammatory bowel disease, eye inflammation, pain in the joints of your arms or legs, or psoriasis?
- Does it feel worse for the first 30 or so minutes from getting up?
- Has it lasted with periods of being on and off for greater than 3 months?
If you answered yes to the majority of these questions, you may have inflammatory pain.
AS often starts in the lower back, but it can progress to other areas and cause additional symptoms. According to the
- pain, stiffness, and inflammation in other joints, such as the shoulders, knees, feet, or ribs
- loss of appetite
- abdominal pain
- changes to vision changes
- eye pain due to uveitis
- trouble taking deep breaths (a sign that your ribs may be affected)
- skin rashes
- loose bowel movements
- weight loss
The following table may help you determine if your back pain is likely mechanical or inflammatory:
|Other symptoms are present.||no||yes|
|Pain improves during exercise.||no||yes|
|Pain improves with rest.||yes||no|
|Pain started after physical exertion or lying on a bad mattress.||yes||no|
|Pain and stiffness last a long time without gradual improvement.||no (in most cases, with rest, your pain should start to improve gradually over time)||yes (pain may go away but will typically come back or flare up)|
Some factors, known as risk factors, can put you at greater risk of having AS-associated back pain.
- Age: AS typically occurs in younger adults under age 45.
- Gender: AS is more likely in men than women.
- Genetics: A family history of the disease can put you at greater risk.
- Other factors: Having inflammatory bowel disease or psoriasis puts you at greater risk.
Getting your back pain properly diagnosed can help with improving your treatment outlook.
Mechanical back pain will typically improve over time with rest. In moderate to severe cases, you may need additional treatment, but you should see improvement with treatments, according to Creaky Joints.
- cold and heat therapy
- physical therapy
- losing weight
- changing posture
- avoiding smoking
- light exercise
- steroid injections
If your back pain is inflammatory, these methods will not work. This is because, despite treatment, your immune system will still produce the inflammatory response — which means you will still experience pain. And since AS is a progressive disease, your symptoms may even worsen over time, potentially causing more serious concerns.
Treatments for AS can include several different therapies to help ease symptoms and prevent or slow disease progression. According to
- janus kinase (JAK) inhibitors
- over-the-counter NSAIDs
AS is also treated with surgery and physical therapy.
Mechanical back pain occurs either due to physical exertion, poor spinal alignment, or even sleeping in an odd position. Inflammatory back pain, such as from AS, occurs when the immune system creates inflammation and attacks the joints in the back.
While both can feel about the same and be either severe or mild, you can look for signs that your back pain may be due to inflammation. Some signs include chronic pain and the presence of other symptoms.
Treatment for both conditions varies. You will likely see your mechanical back pain improve with rest and some basic care. Inflammatory back pain from AS will require ongoing monitoring and treatments to address the underlying inflammation to help improve symptoms and help slow disease progression.