Spondyloarthritis (SpA, sometimes called spondylitis) is an umbrella term for a group of inflammatory conditions that cause arthritis in the spine and other joints. Each type of spondyloarthritis is defined by where inflammation occurs in the body, how advanced it is, whether it’s linked to another disease, and the age when symptoms first appear.

Understanding spondyloarthritis as a family of related diseases can help with earlier diagnosis and treatment. Symptoms often overlap across the different subtypes, but knowing your specific type is important. Certain treatments work better for some forms than others.

What Are the Types of Spondylitis?

The spondyloarthritis family includes several related conditions that cause inflammation in different parts of the body. The location of inflammation helps determine the specific type of SpA.

Spondyloarthritis falls into two main categories:

• Axial spondyloarthritis (axSpA) — This type mainly affects the spine and the joints that connect the spine to the pelvis, called the sacroiliac joints. Pain and stiffness are common, especially in the lower back, hips, neck, and ribs — areas known as the axial skeleton.
• Peripheral spondyloarthritis — This type primarily affects joints and tendons outside the spine, such as the shoulders, knees, ankles, wrists, hands, and feet. It can also cause inflammation in other parts of the body, such as the eyes, skin, or intestines.

Subtypes of axial spondyloarthritis include non-radiographic axial spondyloarthritis (nr-axSpA) and radiographic axial spondyloarthritis (r-axSpA). The latter is also referred to as ankylosing spondylitis.

Some people experience both axial and peripheral symptoms at the same time or at different stages of their condition.

1. Ankylosing Spondylitis/Radiographic Axial Spondyloarthritis

Radiographic axial spondyloarthritis, better known as ankylosing spondylitis (AS), is the best-known type of spondyloarthritis. The term “radiographic” means that changes from inflammation — such as bone damage or fusion — are visible on X-rays.

It typically causes pain and stiffness in the lower back and the sacroiliac joints (where the base of your spine meets your pelvis). The condition can also cause symptoms in other joints, like the shoulders, hips, and knees.

People with AS may also experience the following symptoms:

• Uveitis — Inflammation of the eye that can cause pain, redness, or sensitivity to light
• Dactylitis — Swelling of an entire finger or toe, sometimes referred to as “sausage digit”
• Inflammation in the gastrointestinal tract, sometimes linked to inflammatory bowel disease (IBD)

The typical age of diagnosis for AS is around age 30, and the condition is more common among males, according to Cleveland Clinic.

There’s a strong genetic component to this and other types of spondyloarthritis. Most people diagnosed with AS have a gene called HLA-B27, which can be detected with a blood test, though not everyone with the gene develops AS, and some with AS do not carry the gene.

Your healthcare provider may start treatment with exercise and physical therapy, along with nonsteroidal anti-inflammatory drugs (NSAIDs) to help reduce pain and stiffness.

If symptoms persist, newer biologic medications — such as tumor necrosis factor (TNF) inhibitors or interleukin (IL)-17 inhibitors — may be recommended to control inflammation and prevent long-term damage. Other options can include targeted synthetic drugs (like JAK inhibitors) or short-term corticosteroids for flares.

Over time, ongoing inflammation in AS can lead to new bone formation and spinal fusion (a process called ankylosis), which may reduce flexibility. People with long-standing or advanced disease may also have a higher risk of spinal fractures, since fused areas of the spine can become more brittle.

Early diagnosis and consistent treatment can help prevent or slow these changes.

2. Enteropathic Arthritis

Enteropathic arthritis is a type of spondyloarthritis that occurs in people with IBD, such as Crohn’s disease and ulcerative colitis. Researchers estimate that about 1 in 5 people with IBD develop this form of arthritis. In enteropathic arthritis, inflammation affects both the joints and the digestive tract.

Enteropathic arthritis most commonly causes pain and stiffness in the joints of your arms and legs, but it can also affect the spine. The disease progression varies — symptoms are consistent for some, but others experience flare-ups and periods of remission. The HLA-B27 gene is also linked to enteropathic arthritis, though it’s less commonly found than in AS.

3. Psoriatic Arthritis

Psoriatic arthritis (PsA) can cause inflammatory pain, stiffness, swelling, and progressive damage in any joint in the body. Symptoms are typically cyclical, with flare-ups followed by periods of remission. Symptoms may include:

• Lower back pain
• Dactylitis
• Enthesitis (heel pain)
• Uveitis
• Nail changes, such as pitting or separation from the nail bed
• Fatigue

Researchers estimate that up to 30 percent of those with skin psoriasis will develop psoriatic arthritis. Similar to ankylosing spondylitis, the HLA-B27 gene is common among people with PsA. Having a psoriasis diagnosis is the biggest risk factor for this condition, but it’s possible to have psoriatic arthritis without skin psoriasis, or to be diagnosed before the skin changes appear.

4. Reactive Arthritis

In some people, a bacterial or viral infection triggers the immune system to attack the joints. This type of spondyloarthritis is known as reactive arthritis. Joint pain typically occurs about one to four weeks after the infection, commonly appearing in the ankles, feet, and knees. Reactive arthritis can also cause conjunctivitis (pink eye) and urinary difficulties.

Risk factors for reactive arthritis include being between the ages of 20 and 40, exposure to specific foodborne or sexually transmitted bacteria, and having the HLA-B27 gene.

For most people, reactive arthritis goes away within one year. Treatment options include NSAIDs and steroids to manage symptoms. If there is still an infection, antibiotics may be used. If symptoms don’t go away or are more serious, doctors may use stronger medications like sulfasalazine to help control the disease.

5. Undifferentiated Spondyloarthritis

Some people develop a joint condition that has some symptoms and features of spondyloarthritis, but the symptoms don’t point to a specific type. Cases of spondyloarthritis that don’t precisely fit one of the identified subtypes may be diagnosed as undifferentiated spondyloarthritis.

People with undifferentiated spondyloarthritis typically experience ongoing low back pain that improves with exercise, starting at a relatively young age, usually before 45. They may have heel pain or swelling in their feet or hands.

People with undifferentiated spondyloarthritis may later develop symptoms that result in a diagnosis of another type of spondyloarthritis or another condition altogether.

6. Juvenile Spondyloarthritis

Spondyloarthritis that begins before age 16 is often classified under juvenile spondyloarthritis, specifically the enthesis-related arthritic subtype. Symptoms include:

• Joint pain and stiffness
• Dactylitis
• Uveitis
• Back pain

Researchers estimate that between 1 and 4 children in 1,000 develop this rare condition. Children with juvenile spondyloarthritis may also be diagnosed as having a specific subtype based on their symptoms, such as enthesitis-related arthritis, PsA, or undifferentiated arthritis.

Juvenile spondyloarthritis also strongly correlates with the HLA-B27 gene, although not all children with the gene develop the condition.

Is Spondylosis a Type of Spondylitis?

Spondylosis is not a type of spondyloarthritis. It’s a separate condition with some similarities. Spondylosis is when your spine starts to wear down over time, which can cause back and neck pain, but this type of pain is worse with movement, as opposed to the inflammatory pain from spondylitis that is worse at rest. It’s easy to confuse the conditions since they sound similar and share symptoms.

Can You Have More Than One Type of Spondylitis?

If someone has spondyloarthritis symptoms that fit multiple subtypes, they may be qualified for more than one type of spondyloarthritis.

For instance, if someone had inflammatory spine and hip pain, IBD, and pain in peripheral joints, they could be said to have both enteropathic arthritis and peripheral spondyloarthritis.

As another example, if someone had a skin rash and joint inflammation in their hands and feet, they may initially be diagnosed with psoriatic arthritis. If they developed spondylitis in their spine that caused fusion of the vertebrae, the person may also be diagnosed with ankylosing spondylitis.

What Conditions Can Be Mistaken for Spondylitis?

Many other disorders that feature back pain can be mistaken for conditions in the spondyloarthritis family. Other types of arthritis, namely rheumatoid arthritis, can sometimes be mistaken for spondylitis, as both are inflammatory rheumatic conditions. However, rheumatoid arthritis is associated with the rheumatoid factor antibody.

Why the Diagnosis Matters

Understanding the specific type of spondyloarthritis you have is important, as this will affect the treatment options for your condition. Early treatment may affect the progression of your symptoms and may stop them from worsening.

Conditions in the spondyloarthritis family have overlapping symptoms, and you may experience different symptoms as the disease progresses. Be sure to discuss any changing symptoms with your healthcare provider, as this can help pinpoint your diagnosis and target the best treatments to improve your quality of life.

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