Ankylosing spondylitis is one of many types of arthritis, a condition that affects joints and surrounding tissues.

“Arthritis” is a broad term used to describe several types of conditions that cause inflammation and pain in your joints and surrounding tissues. There are more than 100 types of arthritis, including a subtype called ankylosing spondylitis (AS).

Learn more about the connections between arthritis and AS, including the possible symptoms, causes, and treatment options.

While arthritis and AS are sometimes regarded as completely separate conditions, AS is actually a subtype of arthritis.

Arthritis can cause inflammation in one or several joints, depending on the type. It may also cause inflammation in tissues that surround the affected joint as well as connective tissues. Over time, the inflamed joint may become painful and stiff, affecting your mobility.

AS is a specific type of arthritis that affects your spine. Over time, inflamed joints and ligaments can cause a stiff spine, eventually making it difficult to bend. Left untreated, the vertebrae of your spine may also fuse together, further reducing spinal flexibility.

Both arthritis and AS may cause:

  • joint pain
  • stiffness that’s worse in the morning or after long periods of rest
  • decreased flexibility
  • reduced mobility

Since there are numerous types of arthritis, the exact symptoms vary by subtype. This includes AS.

Symptoms specific to AS include:

  • back pain and stiffness, which may come and go, and worsen at night and in the morning
  • chronic back pain and limited mobility as the condition progresses
  • pain that extends to the hips and buttocks
  • heat and redness along the affected joints

Such symptoms may gradually develop over several weeks or months.

Sometimes AS may also cause joint pain in the:

  • shoulders
  • ribs
  • knees
  • ankles
  • feet

When AS progresses, it can affect other areas of the body, such as your skin, eyes, and digestive system. As such, you might experience additional symptoms, such as:

  • rib pain when taking deep breaths
  • eye pain and vision changes due to inflammation in your eyes
  • skin rashes
  • fatigue
  • abdominal pain
  • diarrhea
  • loss of appetite and unintentional weight loss

Depending on the subtype, arthritis may develop from wear and tear of the joints over time (such as osteoarthritis, or OA), or it may have an autoimmune component, such as rheumatoid arthritis (RA).

While the exact cause of AS is unknown, it’s thought that a combination of genetics and environmental factors may contribute.

Risk factors for arthritis vary based on subtype and may include genetics, age, and preexisting conditions, such as autoimmune diseases. AS may develop during childhood. It’s usually diagnosed before age 45.

Known risk factors for AS may include a family history of this arthritis or a known HLA-B27 gene mutation. Sometimes a virus or other trigger may lead to the development of AS in people who might be genetically predisposed.

The goals of treatment for arthritis and AS are to help reduce pain and stiffness while further stopping progression that might reduce your mobility.

Treatments may include:

  • pain medications
  • medications that decrease inflammation, such as steroids
  • an exercise plan
  • physical therapy
  • dietary changes, such as eating more antioxidant-rich foods
  • weight loss to reduce pressure on the joints
  • surgery for severe joint damage
  • biologic medications (for AS, RA, and other arthritis subtypes)

A doctor may diagnose arthritis and AS with a physical exam as well as imaging tests that look for evidence of joint damage in your body. A doctor will also ask you about your symptoms, including where they occur and how long you’ve had them.

In some cases, blood testing and genetic counseling may be used. For AS, a doctor may recommend testing for the HLA-B27 gene.

Have a doctor look at any chronic pain or stiffness in your joints, especially if it’s getting worse over time. All types of arthritis, including AS, may progress and limit your mobility.

A prompt diagnosis and treatment plan can help you manage such complications.

Arthritis and its subtypes, like AS, are complex. You may have a lot of questions to ask a doctor. Here are some of the most frequently asked questions about these two conditions.

How are ankylosing spondylitis and rheumatoid arthritis different?

Both AS and RA are arthritis subtypes that may develop from a combination of genetics and environment. But while AS affects your spine, RA causes pain, inflammation, and stiffness in multiple joints throughout your body. Fatigue and fever are other possible RA symptoms.

How are ankylosing spondylitis and osteoarthritis different?

While both AS and OA are arthritis subtypes, long-term wear and tear to an affected joint largely causes OA. OA is also the most common type of arthritis, affecting an estimated 32.5 million U.S. adults.

With OA, you may experience joint pain and stiffness along with decreased flexibility. This arthritis subtype commonly affects the hips, knees, and hands.

How are spondylitis and osteoporosis different?

AS is a type of arthritis that causes inflammation and pain in your spine. While osteoporosis may also affect your spine, it’s a degenerative bone disease that causes a loss of bone mass and strength. Osteoporosis can also lead to bone fractures.

AS is one of the many subtypes of arthritis, which causes joint pain, stiffness, and inflammation.

If you have a family history of AS, or if you’re experiencing ongoing pain and stiffness along your back that extends to your hips, you may consider talking with a doctor regarding next steps. Treatment may consist of medications combined with therapy and an exercise plan.