Spondyloarthritis refers to a number of different inflammatory diseases that affect the joints in your spine and surrounding areas and can also potentially cause symptoms in other areas of your body.
Probably the best-known diseases under the spondyloarthritis umbrella are ankylosing spondylitis — which typically affects your spine and sacroiliac (SI) joints, where your spine connects to your pelvis — and psoriatic arthritis, which tends to affect your skin and small joints in your hands and feet.
But there’s much more to spondyloarthritis than the classic symptoms of lower-back pain and stiffness associated with ankylosing spondylitis. Different diseases in this category can affect not just your back and hips but also your shoulders, hands, knees, toes, eyes, skin, digestive tract, and reproductive organs.
That list of affected areas might sound almost absurdly broad, but there are some common traits that all forms of spondyloarthritis share. Here’s what you should know about this category of diseases and how doctors try to sort through the sometimes confusing mix of symptoms to arrive at an accurate diagnosis.
Types of Spondyloarthritis
All types of spondyloarthritis have the potential to cause symptoms — such as pain and stiffness — in your spine due to inflammation. But some types are actually defined by symptoms outside your spine. This difference is the basis for two broad categories of spondyloarthritis: axial and peripheral.
“Axial means you have disease that is concentrated in your spine and SI joints, or the center of your body,” explains Jean Liew, MD, a senior fellow and spondyloarthritis researcher in the division of rheumatology at the University of Washington School of Medicine in Seattle. “And peripheral is if your disease is really focused on joints that are not in the spine, like your limbs — swelling in your knees, hands, or wrists, things like that.”
It’s not uncommon, Dr. Liew notes, for a single person to have symptoms that point to both categories of disease. In that case, she says, your diagnosis will be based on which symptoms are predominant.
Types of axial spondyloarthritis include:
Ankylosing Spondylitis (AS) Characterized by pain and stiffness in the lower back caused by enthesitis, or inflammation of the ligaments connecting bone to bone, AS can eventually cause sections of your spine to fuse together (known as ankylosis) if left untreated. Involvement of the SI joints can typically be seen on an X-ray in AS.
Non-Radiographic Axial Spondyloarthritis (nr-axSpA) Symptoms of nr-axSpA are similar to those of AS, with the key difference being that joint damage cannot be seen on X-ray images. Instead, magnetic resonance imaging (MRI) may be used to assess inflammation.
Types of spondyloarthritis that often — but not always — can be labeled as peripheral (depending on your exact symptoms) include:
Psoriatic Arthritis (PsA) Symptoms of PsA commonly include pain and swelling in the hands and feet, along with a psoriasis skin rash. Some people also have pain or stiffness in their spine.
Enteropathic Arthritis (EnA) This form of spondyloarthritis affects people with inflammatory bowel disease (IBD), which includes Crohn’s disease and ulcerative colitis. People with EnA will have gastrointestinal (GI) symptoms like chronic diarrhea, blood in the stool, or abdominal pain, along with pain or stiffness in the spine or other joints.
Reactive Arthritis (ReA) Following an infection — often in the intestine or urinary tract — symptoms like pain or swelling in the spine, other joints, skin, eyes, bladder, reproductive organs, or other areas of the body may develop in ReA. These symptoms typically go away after a few months but may come back later.
Undifferentiated Spondyloarthritis (USpA)
This form of spondyloarthritis may be diagnosed if symptoms don’t fit the pattern of other categories — such as when someone has joint pain outside the spine along with pain and swelling in soft tissues, but no back pain, psoriasis, bowel symptoms, or recent infection.
Juvenile Spondyloarthritis (JSpA)
Another type of spondyloarthritis that’s officially classified separately from all of the above is juvenile spondyloarthritis (JSpA), also known as enthesitis-related juvenile idiopathic arthritis (JIA). This simply refers to spondyloarthritis that’s diagnosed in children or teenagers and can look like any type of disease. But peripheral symptoms — especially in the legs and feet — are often the initial signs of disease in this age group, according to the Spondylitis Association of America.
How Spondyloarthritis Is Diagnosed
Diagnosing spondyloarthritis isn’t always easy, especially since it can cause symptoms in many different areas of the body. But there are a number of factors that tend to separate spondyloarthritis from other forms of arthritis or other conditions entirely.
One important distinction for doctors to make is between inflammatory and noninflammatory back pain. With inflammatory back pain — the kind seen in spondyloarthritis — “the stiffness and symptoms tend to be worse first thing in the morning or after prolonged immobility,” and improve with movement, according to Natalie E. Azar, MD, a rheumatologist at NYU Langone Health in New York City.
Dr. Azar says that in both the spine and other areas of the body, “stiffness would typically be more profound or prolonged in an inflammatory condition” than in a noninflammatory condition — such as osteoarthritis, which is more closely related to “wear and tear” of cartilage in joints than to inflammation. “The swelling might be more, the pain might be more” in inflammatory conditions, she adds.
Of course, spondyloarthritis isn’t the only type of inflammatory arthritis, so it’s still necessary to look at other factors once this category is suspected or established. One potential clue to spondyloarthritis is that it’s negative for classic rheumatoid arthritis antibodies. This distinguishes it, Azar notes, from most cases of rheumatoid arthritis (RA), another type of inflammatory arthritis.
Probably the most important factor that distinguishes spondyloarthritis from other diseases that may have overlapping symptoms, Azar says, is involvement of the entheses — the areas where ligaments and tendons attach to bone. To look for this type of soft-tissue inflammation — known as enthesitis — “you basically press at the inside or outside of the elbow, at the Achilles tendon or plantar fascia [ankle or heel], and the outside of the hip,” Azar explains. “If there’s tenderness there, or sometimes you can see swelling,” then it’s likely the person has enthesitis.
Of course, diagnosing any type of spondyloarthritis also means getting the most complete picture possible of a person’s symptoms and health history. “You’re asking about skin symptoms, GI symptoms, musculoskeletal symptoms,” says Azar. “It’s really important to ask about personal and family history, especially of psoriasis and IBD.”
Guiding Treatment for Spondyloarthritis
There are two main types of drug treatments for spondyloarthritis: nonsteroidal anti-inflammatory drugs (NSAIDs) and biologic therapies. Most treatment guidelines suggest prescribing an NSAID first, but your doctor may decide to prescribe a biologic drug first, depending on your symptoms — especially if a response to the drug may help clarify that your condition is inflammatory in nature.
While prescribing a drug to help clarify a diagnosis isn’t part of any official guidelines, “in the real world, that’s what people often end up doing,” says Liew. “I still wouldn’t say it’s diagnostic. Everything just shifts your suspicion higher or lower.”
It’s very important to find out if someone with spondyloarthritis has bowel symptoms that may suggest IBD, says Azar, because effective treatment of IBD often leads to resolution of other symptoms like joint pain. Even subtle bowel symptoms may warrant a referral to a gastroenterologist before proceeding further with treatment. While there’s some overlap between biologic therapies for spondyloarthritis and IBD, “there are nuanced differences” in treatment approaches, she notes.
But drugs aren’t the only important element of treatment for spondyloarthritis. “Physical therapy and exercise are key for inflammatory arthritis, and especially spondyloarthritis,” says Liew. “If you look at the guidelines, it’s a thing that’s constant no matter if your disease is superactive or well controlled.”
When it comes to both diagnosing and treating spondyloarthritis, a rheumatologist’s job is to get as much information as possible to guide a decision, says Azar. “It’s not just one thing. You start listening to the story, and then you dive deeper.”