How Psoriatic Arthritis Causes Back Pain — and What to Do About It

Although psoriatic arthritis most often involves smaller joints in your fingers, toes, wrists, knees, or ankles, it can also affect your spine.

Inflammation around the ligaments that hold the spine together can cause back pain.iStock

Psoriatic arthritis is known for causing peripheral arthritis, or pain in the joints of the hands, wrists, knees, and ankles. But the condition can also affect the spine and pelvis, causing back pain. In fact, back pain is very common in people with psoriatic arthritis, says John Davis, III, MD, a clinical rheumatologist who specializes in psoriatic arthritis and axial spondyloarthritis at the Mayo Clinic in Rochester, Minnesota.

How Psoriatic Arthritis Can Affect the Spine

Psoriatic arthritis is a chronic inflammatory condition that can cause pain and stiffness in any joint in your body or anywhere the ligaments and tendons connect to bone. When psoriatic arthritis specifically affects the joints in the vertebrae of the spine, it’s known as spondylitis or axial arthritis. Sacroiliitis is when psoriatic arthritis affects the joints between your pelvis and spine, known as your sacroiliac joints.

“Spondylitis leads to inflammation around the ligaments that hold the spine together,” causing back pain, says Rajat Bhatt, MD, a rheumatologist at Prime Rheumatology in Texas. The condition causes abnormal bone growth and erosion between the vertebrae that may cause them to merge, which can decrease your range of motion.

But back pain can have other causes in people with psoriatic arthritis. “[If] patients are overweight or obese and sedentary, mechanical back pain [can] coexist with psoriatic arthritis,” explains Dr. Bhatt.

How Common Is Spondylitis in People Who Have Psoriatic Arthritis?

According to the National Psoriasis Foundation, spondylitis affects 7 to 32 percent of people living with psoriatic arthritis. However, these estimates may be low. “Among patients with psoriatic arthritis, the presence of axial involvement, including sacroiliitis and spondylitis, is probably underrecognized,” explains Dr. Davis. In fact, a 2021 review reported that axial disease in people with psoriatic arthritis could be as high as 70 percent.

According to the Arthritis Foundation, most people who have psoriatic arthritis are diagnosed with spondylitis before the age of 40, although the condition can appear later in life. And psoriatic arthritis–related back pain is more common in men than women.

People with axial arthritis may also experience more joint damage and nail changes from psoriatic arthritis. A 2018 study analyzed 1,530 people with psoriatic arthritis and found that the 12.5 percent who had spondylitis were also more likely to have enthesitis, or inflammation where tendons and ligaments attach to bone.

Symptoms of Psoriatic Arthritis in the Spine

According to Davis, when psoriatic arthritis affects the spine, you may experience:

  • Back pain that gets worse with rest and better when you’re moving
  • Back stiffness in the morning that lasts at least 30 minutes
  • Inflammatory pain around your hips and butt (your sacroiliac joints)
  • Reduced range of motion

Back pain can persist for up to 10 years before it’s linked to psoriatic arthritis or another related disease, says the Arthritis Foundation. According to a 2020 review, the delayed diagnosis can lead to unchecked inflammation and structural damage. A magnetic resonance imaging (MRI) scan allows your doctor to see changes in the bones and soft tissues of the spine and pelvis to diagnose spondylitis.

How to Tell if Back Pain Is Related to Psoriatic Arthritis or Something Else

If your back is bothering you, it’s important to check in with your doctor to get to the root cause.

Ankylosing spondylitis is one condition that’s often confused with psoriatic arthritis. “Both psoriatic arthritis and ankylosing spondylitis are in the family of ‘spondyloarthritis’ and are highly related,” explains Davis. Ankylosing spondylitis is another type of inflammatory arthritis. It causes the vertebrae in the spine to fuse, resulting in back pain.

People with ankylosing spondylitis are more likely to lose spinal mobility than those with axial-psoriatic arthritis, although the latter may lose range of motion. Most people with axial-psoriatic arthritis also have pain in their peripheral joints — hands, feet, ankles — but it’s possible to experience back pain only.

Ultimately, imaging of your back will help your doctor determine whether you have axial-psoriatic arthritis or ankylosing spondylitis. “Although there is overlap, there are some subtle differences in the appearances of X-ray changes in both the sacroiliac joints and the spine,” explains Davis.

Another common cause for discomfort is mechanical back pain, which is linked to an injury. If you’re obese, it may be caused by added weight on your spine. Unlike spondylitis, which is usually better when you move and worse with rest, mechanical back pain is worse when you move and better with rest, according to both Davis and Bhatt. Mechanical back pain also tends to cause brief back stiffness when you wake up, whereas spondylitis causes lingering morning stiffness, Davis adds.

That said, it’s easy to mistake symptoms of one condition for the other. “What appears to be mechanical pain could be inflammatory pain, and what appears to be inflammatory pain could be mechanical pain,” says Bhatt.

People who have psoriatic arthritis may also have back pain linked to a number of other causes, says Davis, including:

  • osteoarthritis of the spine, also known as degenerative joint disease of the spine
  • spinal stenosis, or the narrowing of spaces in your spine that triggers nerve pain
  • fibromyalgia, or widespread musculoskeletal pain that’s thought to happen when the brain processes pain differently than normal
  • central sensitization, a condition where the central nervous system amplifies the sensation of pain

“It’s a very complex topic, so it’s best to ask a doctor,” says Bhatt. “There are certain tests your doctor can run to confirm the right diagnosis.”

How Psoriatic Arthritis in the Spine Is Treated

If you think you might have spondylitis, talk to your doctor. Early treatment reduces the risk of progressive loss of spinal mobility and function. A number of treatments can help reduce pain and other symptoms associated with spondylitis in people with psoriatic arthritis, including:

You’ll likely be on at least one of these treatments long term, because odds are good that it will work. “Most patients improve, and we see fairly high rates of remission,” says Davis.

Additional reporting by Nina Wasserman.