Differences between rheumatoid arthritis (RA) and ankylosing spondylitis (AS) include the joints they affect and who are most likely to develop each condition. Some treatments may work for one but not the other.
Rheumatoid arthritis (RA) and ankylosing spondylitis (AS) are among the most common rheumatic (joint) conditions.
RA and AS are both types of arthritis, but symptoms and treatment are different.
RA is an autoimmune disorder that causes joint pain and inflammation. It most commonly affects the joints in your hands, wrists, and knees.
AS is also an autoimmune disorder. It primarily causes pain and inflammation in the joints of your spine.
Read on to learn about the similarities and differences between RA and AS, including their diagnoses and the symptoms, treatments, and outlooks for people who have them.
RA
- hands
- wrists
- knees
RA can also affect other joints, including in your:
A hallmark of RA is symmetrical involvement. That means it usually affects joints in both extremities. For example, it would affect both of your wrists or both knees.
RA doesn’t usually affect the joints of your spine. One
When AS affects non-spine joints, it’s usually symmetrical, but there can be exceptions.
Symptoms of both of RA and AS can include:
- stiffness in your joints, especially in the morning
- low grade fever
- fatigue
- loss of appetite
- unexplained weight loss
RA can also cause symptoms such as:
- pain, stiffness, tenderness, and swelling in joints of your extremities
- symptoms in more than one joint
- symptoms that begin in smaller joints, such as your fingers or toes
AS can also cause symptoms such as:
- severe back pain
- problems with posture or stooped shoulders
- pain, stiffness, tenderness, or swelling that affects large joints outside of your spine
Learn more about conditions that can cause joint pain.
RA and AS occur in around
RA is more common in people assigned female at birth, while AS is more common in people assigned male at birth. AS usually begins before 30 years of age. RA typically happens later, between 40 and 50 years of age.
Other risk factors for RA
- smoking and secondhand smoke exposure
- obesity
- lung disease
- periodontitis
Other risk factors for AS
- Crohn’s disease
- ulcerative colitis
- psoriasis
Can a person have both RA and AS?
It’s pretty rare for people to have both RA and AS at the same time. This is because these conditions have different mechanisms of development.
Still, it’s not impossible. A 2021 Chinese study observed 22 people with both RA and AS in a span of 6 years.
Diagnosing both RA and AS can be a lengthy process, requiring multiple labs and imaging tests. This is because these conditions can have overlapping symptoms with other joint disorders, and no single test can identify either AS or RA.
The first step in diagnosing either condition is usually a physical exam. A doctor will ask about your symptoms, medical and family history, and risk factors. They’ll check your joints for swelling, tenderness, and range of motion.
They may then order imaging and blood tests.
- X-rays: X-rays help a doctor to assess the extent of inflammation in your affected joints and bones.
- MRI: Doctors use MRI for a more detailed look inside your affected joints.
- Ultrasound: Ultrasounds create a “map” of affected bones, joints, and tendons.
Blood tests include:
- Complete blood count (CBC): A CBC helps to confirm or rule out anemia and other blood conditions associated with certain joint disorders,a
- Erythrocyte sedimentation rate (ESR) test: An ESR test can help identify the extent of inflammation in your blood.
- C-reactive protein (CRP) test: A CRP test measures inflammation.
- Antinuclear antibody (ANA) test: An ANA test looks for evidence of an autoimmune condition, which may help diagnose or rule out other possible causes of your symptoms, such as lupus, scleroderma and juvenile arthritis.
- Rheumatoid factor test: A rheumatoid factor test can help distinguish RA from other conditions.
- HLA-B27 test: An HLA-B27 test can detect a genetic marker common in AS.
Rheumatologists, doctors who treat joint conditions, use a treatment strategy called “treat-to-target (T2T)” when managing both RA and AS. T2T involves setting a treatment target and following a strict monitoring protocol with necessary adjustments to reach the target.
Doctors
Medications that may be suitable for treating AS
- biologics such as leflunomide, methotrexate, and sulfasalazine
- corticosteroids
- disease-modifying antirheumatic drugs (DMARDs)
- Janus kinase (JAK) inhibitors
For RA, doctors
- corticosteroids
- biologics
- JAK inhibitors
Physical therapy and occupational therapy can help both conditions.
Surgery may be necessary in severe cases of AS or RA.
It’s difficult to estimate the outlook for people with either RA or AS because it depends on many factors.
While neither RA nor AS is fatal, living with RA or AS can significantly affect your quality of life, mental health, and emotional well-being.
Your doctor can help you find ways to manage your symptoms and improve your quality of life.
Here’s a quick summary of the key similarities and differences between RA and AS.
| Rheumatoid arthritis | Ankylosing spondylitis | |
|---|---|---|
| Who gets it? | • more common in people assigned female at birth • usually begins after | • more common in people assigned male at birth • usually begins before 30 |
| Symptoms | • pain/swelling in joints of your extremities • begins in smaller joints | • severe back pain • pain or swelling in large joints outside of your spine |
| Diagnosis | • physical exam • imaging • blood tests, | • physical exam • imaging • blood tests, |
| Treatment | • NSAIDs • corticosteroids • biologics • JAK inhibitors | • NSAIDs • biologics • corticosteroids • DMARDs • JAK inhibitors |
Rheumatoid arthritis (RA) and ankylosing spondylitis (AS) are different types of arthritis. Although related, they have different symptoms and causes.
However, these conditions do have many similarities. Your doctor will likely need to order numerous tests to confirm the diagnosis.
Treatment of RA and AS is similar, but there are key differences. In general, nonsteroidal anti-inflammatory drugs (NSAIDs), biologics, corticosteroids, and JAK inhibitors may help. Your doctor may also recommend physical therapy, occupational therapy, and, in severe cases, surgery.