If you have chronic low back pain, arthritic changes to your sacroiliac joint may be the cause. Experts estimate 1 Cohen SP, Chen Y, Neufeld NJ. Sacroiliac joint pain: a comprehensive review of epidemiology, diagnosis and treatment. Expert Rev Neurother. 2013 Jan; 13(1):99-116. 15% to 30% of all low back pain cases originate at the sacroiliac joint, or SI joint. Many types of arthritis can affect the SI joint.

The first symptom of ankylosing spondylitis is often pain in the sacroiliac joint. Watch: Ankylosing Spondylitis Video

Sacroiliac joint anatomy

Most people are aware that the spine is made up of bones called vertebrae, and that the vertebrae in the lower spine are called lumbar vertebrae. However, many are unaware of the wedge-shaped bone that the lumbar vertebrae rest upon, known as the sacrum.

On either side of the sacrum is a sacroiliac joint that connects it to the pelvic bone. The sacroiliac joints are among the largest synovial joints in the human body, providing a large potential target of attack by various forms of arthritis.

Read more about Sacroiliac Joint Anatomy on Spine-health.com.

Symptoms of sacroiliac joint pain

Patients with SI joint pain often report diffuse pain of the low back, buttocks, hips, and/or the groin region. In addition, sacroiliac pain can radiate down the legs, most commonly along the back of the thighs.


Types of arthritis associated with sacroiliitis

Arthritic diseases cause painful joint inflammation, and inflammation in the SI joint is known as sacroiliitis. Types of arthritis associated with sacroiliitis include:

1. Osteoarthritis

More than 32 million Americans have symptoms of osteoarthritis (OA), 2 Centers for Disease Control and Prevention, National Center for Disease Prevention and Health Promotion. Osteoarthritis (OA). Last reviewed February 28, 2020. Accessed March 5, 2020. https://www.cdc.gov/arthritis/basics/osteoarthritis.htm which is defined as a breakdown of cartilage in a joint. This breakdown can lead to complications that result in pain, swelling, and difficulty with movement.

Given the vital role that the large SI joint plays in transferring upper body weight to the lower extremities, it is commonly affected in osteoarthritis. People who have osteoarthritis in their SI joints often develop osteophytes or bone spurs around the joint, leading to pain and dysfunction.

See What Is Hip Osteoarthritis?

2. Rheumatoid arthritis (RA)

While initial symptoms of rheumatoid arthritis typically affect smaller joints, such as the hands and wrists, it is possible for the sacroiliac joint to be affected, too.

RA is a condition in which the immune system attacks various joints in the body, resulting in joint inflammation. The normally delicate lining that surrounds the joints (called synovial lining) can become abnormally thickened. Symptoms include joint pain, swelling, and stiffness, and may also include fatigue and flu-like symptoms.

See What Is Rheumatoid Arthritis (RA)?

3. Lupus (SLE)

Many regions of the body can be affected by lupus, including skin, blood, kidneys, brain, other organs, as well as joints. Women in the age range of 15 to 44 years have the highest risk of being diagnosed with the most common subtype of the condition, systemic lupus erythematosus (SLE). 3 Office on Women’s Health, Lupus in Women. Centers for Disease Control and Prevention. Last reviewed October 17, 2018. Accessed March 5, 2020. https://www.cdc.gov/lupus/basics/women.htm Many patients with SLE develop SI joint pain as one of their symptoms.

4. Ankylosing spondylitis (AS)

This form of autoimmune arthritis causes inflammation of joints, ligaments, and tendons. Frequently, SI joint pain and spontaneous spinal joint fusion are the initial presenting symptoms for patients with ankylosing spondylitis.

An interesting difference from other autoimmune conditions is that AS predominantly impacts males—Men are 2 to 3 times more likely to get ankylosing spondylitis than women. 4 Dean LE, Jones GT, Macdonald AG, Downham C, Sturrock RD, Macfarlane GJ. Global prevalence of ankylosing spondylitis. Rheumatology (Oxford). 2014;53(4):650-7.

See What Is Ankylosing Spondylitis?

5. Psoriatic arthritis

Like ankylosing spondylitis, psoriatic arthritis is a chronic autoimmune disease. It is closely associated with a skin condition called psoriasis, but not everyone who has psoriatic arthritis also gets psoriasis.

Psoriatic arthritis commonly affects the joints of the spine, including the SI joints. In fact, medical studies report the prevalence of sacroiliitis in patients with psoriatic arthritis to be between 34% and 78%. 5 Krawczyk-Wasielewska A, Skorupska E, Samborski W. Sacroiliac joint pain as an important element of psoriatic arthritis diagnosis. Postepy Dermatol Alergol. 2013;30(2):108–112. doi:10.5114/pdia.2013.34161 Patients with psoriasis and chronic lower back pain should consider having a sacroiliac joint assessment with a musculoskeletal specialist.

See What Is Psoriatic Arthritis?

6. Gout and pseudogout

While the most common site for gout attacks is the big toe, the sacroiliac joint(s) can also be affected.

Gout occurs when needle-like, microscopic crystals collect in the soft tissues of the joint. The crystals, called uric acid crystals, can cause joint pain as well as swelling, redness, and warmth. The build-up of uric acid crystals occurs if the body cannot adequately metabolize purines, a chemical compound found in many foods.

See All About Gout - Symptoms, Diagnosis, Treatment

Pseudogout also develops as a result of microscopic crystals. Doctors often refer to pseudogout as calcium pyrophosphate deposition (CPPD) or acute calcium pyrophosphate crystal arthritis (acute CPP crystal arthritis).

See All About Pseudogout - Symptoms, Diagnosis, Treatment

If you have been diagnosed with gout or pseudogout and you have lower back pain, consider the possible connection with your doctor.

7. Reactive arthritis

Inflammation of the sacroiliac joint and/or other parts of the spinal column are common symptoms of reactive arthritis. Reactive arthritis is triggered by an infection, and in most cases, the infection has resolved by the time reactive arthritis symptoms appear. People who have reactive arthritis may also notice symptoms that affect their eyes and fingers.

See Reactive Arthritis Survival Guide

Of course, not all sacroiliac pain is caused by arthritis.


Other potential causes of SI joint pain

In addition to arthritis, SI joint pain may be caused by:

  • Traumatic injuries, such as falls and other accidents
  • Repetitive SI joint biomechanical stress such as repeated heavy lifting, prolonged intense physical activity, and manual labor
  • Prolonged sitting or standing, particularly if the pelvic and/or low back muscles are weak and unstable
  • Pregnancy, which causes the relaxing of ligaments and instability
  • Added stress to the SI joint from another cause or procedure, such as a lumbar spinal fusion surgery

Due to the many possible causes of sacroiliac joint pain, it is essential to have a complete assessment of your condition by a qualified medical professional. Contact either your primary care provider, orthopedist, or other musculoskeletal specialist for more information regarding your individual situation.

Learn more:

Possible Causes of Sacroiliitis and SI Joint Pain

Understanding Joint Pain

Dr. Keley John Booth, MD, is a board-certified Diplomat of the American Board of Anesthesiology and specializes in interventional pain management. Dr. Booth received his medical doctorate degree from the University of Oklahoma and completed an anesthesiology residency at the University of Oklahoma Health Sciences Center.