Psoriatic arthritis (PsA) and sacroiliitis are both inflammatory conditions that affect your joints. That said, each may affect your body differently.

Psoriatic arthritis (PsA) is a chronic autoimmune disorder where the immune system mistakenly attacks the healthy joints in your body, leading to inflammation.

PsA affects nearly 20% of people with psoriasis, a condition involving scaly, dry, and itchy skin plaques.

Sacroiliitis is also an inflammatory joint condition. However, it specifically affects the sacroiliac joints, which connect the ilium (the bone at the top of your pelvis) to the sacrum (the lower part of your spine).

Keep reading to learn more about how these two conditions are connected and how to manage joint pain.

PsA and sacroiliitis are both inflammatory conditions that affect certain joints in your body.

According to the Arthritis Foundation, PsA most commonly causes symptoms in the joints of your:

  • fingers
  • toes
  • knees
  • ankles

However, research suggests that up to 70% of people living with PsA also have axial involvement.

The axial skeleton consists of 80 bones that make up your spine, head, neck, and chest. This includes the sacroiliac joints, which help support the weight of your upper body as you walk.

Sacroiliitis is inflammation of one or both of the sacroiliac joints in the lower back.

A 2023 review suggests that up to 50% of people with PsA have sacroiliitis. Similarly, the authors of a small 2020 study note that sacroiliac inflammation is one of the first signs of PsA.

However, the link between PsA and sacroiliitis isn’t fully understood.

Researchers suggest that some risk factors may increase your chance of developing axial involvement if you have PsA, including:

Sacroiliitis describes inflammation that affects specific joints in your lower back (the sacroiliac joints).

PsA is an inflammatory autoimmune disease that may cause inflammation in joints and ligaments throughout the body. It most often affects the hands and feet but can sometimes affect the pelvis and lower back.

PsA is one of several conditions that cause sacroiliitis. Other conditions that may result in sacroiliitis include:

Injury, pregnancy, and infection are also sometimes responsible for sacroiliitis.

Symptoms of PsA usually affect the smaller joints like the fingers and toes, but they could also affect other parts of your body. Swelling and pain may affect only one joint or multiple joints.

PsA symptoms may include:

  • pain, tenderness, stiffness, and swelling in your joints and tendons
  • reduced range of motion
  • fatigue
  • pitting and other changes to your nails
  • redness and pain in your eye

The main symptom of sacroiliitis is pain in your lower back, buttocks, hips, or thighs. The pain may feel dull and achy or sharp and stabbing, and it can radiate down your legs.

It typically hurts more when you sit or stand for a long period, climb stairs, or stand up from a chair.

Without treatment, PsA and sacroiliitis may progress and cause permanent joint damage. Speak with a healthcare professional if you experience symptoms. They could provide a proper diagnosis and treatment plan.

There’s no specific test to diagnose PsA and sacroiliitis.

A healthcare professional will first perform a medical history and physical examination of your symptoms. They’ll typically order several imaging and blood tests to help eliminate other conditions. These tests may include:

It can be challenging to diagnose sacroiliitis because many other conditions also cause lower back pain. Having PsA is one clue that can point a doctor to a sacroiliitis diagnosis since the two conditions often exist together.

Treatment for PsA and sacroiliitis aims to help reduce inflammation, relieve pain, and stop disease progression. Your treatment plan may include:

Can psoriatic arthritis affect the sacroiliac joint?

Yes, psoriatic arthritis may affect the sacroiliac joint.

What autoimmune disease causes sacroiliitis?

Research suggests that several autoimmune conditions may lead to sacroiliitis, including psoriasis, psoriatic arthritis, ankylosing spondylitis, inflammatory bowel disease (IBD), and rheumatic disease.

Can a rheumatologist treat sacroiliitis?

Yes, a rheumatologist can help treat sacroiliitis because they are specialists in conditions that affect the muscles, joints, and bones.

What is sacroiliitis a hallmark of?

The most common cause of sacroiliitis is axial spondyloarthritis (AxSpA). This is a type of arthritis that affects your axial system, which includes your spine.

PsA is an autoimmune disease that may cause inflammation in joints throughout the body. It can sometimes cause sacroiliitis, an inflammation in the joints of the lower back.

Speak with a doctor if you have pain in your lower back, legs, or hips. They could provide a proper diagnosis.

If you have PsA or sacroiliitis, it’s important to begin treatment to reduce inflammation in your joints. Early treatment can prevent long-term complications and permanent joint damage.