Ankylosing spondylitis (AS) is a type of arthritis that causes inflammation in the joints and ligaments in the spine. It can cause a person’s bone marrow to swell. Other symptoms include back pain, stiffness, loss of mobility, and fatigue.

AS affects the lower part of the spine and the sacroiliac joints, which are the joints where the spine meets the hips. The inflammation can move up to the spine and involve the thoracic and cervical spine.

Inflammation from AS causes a person to experience joint pain, stiffness, and a loss of mobility in the spine and lower back.

This article looks at how AS can cause swelling in the bone marrow.

The back of a person with AS who has bone marrow edema.Share on Pinterest
Jess Craven/Getty Images

Bone marrow edema is the medical term for swelling in the bone marrow. People with AS have a higher risk of developing bone marrow edema than those without AS.

Osteoporosis is a common complication of AS. It is a condition that causes a person to develop bone loss, which causes their bone mass density to decrease. Over 50% of people receiving screening for AS have low bone mass density.

One 2016 study stated that bone marrow edema was more common among those with AS with low bone mass density than in those without low bone mass density.

Osteoporosis has links to an increased risk of bone marrow edema in people with AS.

Medical professionals do not fully understand the causes of osteoporosis in individuals with AS. However, it may have links to inflammation.

One 2016 study states that bone inflammation may lead to increased bone resorption and a low bone marrow density. It adds that bone marrow edema that appears on MRI scans reflects the acute inflammatory changes in the bone.

If a person’s AS causes them to develop bone marrow edema, they may experience severe pain that limits their daily activities.

People may experience pain and swelling that can occur suddenly during rest and activity.

Bone marrow edema may also cause swelling in the joints.

Other symptoms of AS

AS most commonly causes a person to experience lower back pain, hip pain, and stiffness.

If an individual’s AS develops, it may start to progress to other areas of the spine.

Other joint-related symptoms include:

  • impaired mobility
  • postural abnormalities
  • buttock pain
  • hip pain
  • peripheral arthritis
  • inflamed bones
  • dactylitis, which refers to swollen fingers or toes

AS can also affect other areas of the body and can cause several other symptoms, including:

  • pain, inflammation, and stiffness in the ribs, shoulders, feet, or knees
  • difficulty taking deep breaths if it affects the rib joints
  • inflammation in the eye, which can cause changes to a person’s vision
  • fatigue
  • loss of appetite
  • weight loss
  • rashes on the skin
  • abdominal pain
  • diarrhea

A 2021 article notes that bone marrow edema is typically self-limiting and that treatment involves managing the symptoms.

This can include physical therapy and taking nonsteroidal anti-inflammatory drugs (NSAIDs) to help reduce the pain and inflammation.

According to the American Physical Therapy Association, physical therapists can improve a person’s quality of life through prescribed exercise, hands-on care, and client education.

Physical therapists can also examine an individual’s symptoms and develop a treatment plan to improve their symptoms, manage pain, restore function, and improve their ability to move.

Treatments for AS

The first-line treatment of AS pain is with NSAIDs.

Other possible medications for treating AS include:

  • Biologics: These are medications that target specific immune messages. They interrupt signals that can help reduce or prevent inflammation. Tumor necrosis factor-alpha inhibitors (TNF-I’s) are a type of biologic medication. Tumor necrosis factor (TNF) is a substance in the body that helps fight infections. If a person has an autoimmune disease, such as AS, then high levels of TNF can cause inflammation, leading to painful symptoms. TNF-I’s prevent this inflammatory response, which can reduce AS symptoms, such as bone marrow edema.
  • Janus kinase (JAK) inhibitors: These medications send messages to cells to stop inflammation from within the cell itself.
  • Corticosteroids: These medications can reduce inflammation and can provide a person with pain relief. Corticosteroids are powerful drugs, so doctors will often avoid high and regular doses to avoid side effects.

To diagnose bone marrow edema relating to AS, a healthcare professional may order the following imaging tests:

MRI scans may detect bone marrow edema 2 days after a person first experiences symptoms.

If a person experiences the symptoms of bone marrow edema or AS, they should speak with a doctor.

AS is a rare condition, so individuals may wish to consult doctors or healthcare professionals who have experience with this disease.

A person can find these specialists through:

  • advocacy organizations
  • clinical trials
  • articles in medical journals
  • universities or tertiary medical centers

If they cannot find a specialist in their local area, they may wish to contact national or international specialists. These healthcare professionals may refer the individual to a relevant specialist or consult with a person’s doctor over the phone.

AS is a type of arthritis that causes inflammation in the joints and ligaments in the spine.

AS causes symptoms such as back pain, stiffness, loss of mobility, and fatigue. It may also cause a person’s bone marrow to swell. The medical term for swollen bone marrow is bone marrow edema.

Some medical professionals link bone marrow edema in AS patients to reduced bone mass density. Studies show that over 50% of people receiving screening for AS have low bone mass density.

Treatments for AS and bone marrow edema include medications and physical therapy.