Understanding Sacroiliitis: Is it a Type of Arthritis?

Both sacroiliitis and arthritis end with the suffix “itis,” which means inflammation. Sacroiliitis affects the sacroiliac (SI) joint, and while it’s not a type of arthritis, it is linked to inflammatory arthritis of the spine. ¹ Baronio M, Sadia H, Paolacci S, et al. Etiopathogenesis of sacroiliitis: implication for assessment and management. Korean J Pain. 2022;33(4):294-304. http://doi.org/10.3344/kjp.2020.33.4.294

What is the difference between sacroiliitis and arthritis?

Sacroiliitis refers to the inflammation of the SI joint, which is located on each side of the sacrum (lower spine) and connects the base of the spine to the hip bone. ¹ Baronio M, Sadia H, Paolacci S, et al. Etiopathogenesis of sacroiliitis: implication for assessment and management. Korean J Pain. 2022;33(4):294-304. http://doi.org/10.3344/kjp.2020.33.4.294

• This condition causes the SI joint to become inflamed due to trauma, infection, pregnancy, and arthritis. ¹ Baronio M, Sadia H, Paolacci S, et al. Etiopathogenesis of sacroiliitis: implication for assessment and management. Korean J Pain. 2022;33(4):294-304. http://doi.org/10.3344/kjp.2020.33.4.294
• Sacroiliitis typically causes a dull, aching pain that presents acutely and often has a sudden onset in the lower back, buttocks, and legs that increases when sitting for long periods and/or during activities that involve bending or twisting at the hip. ¹ Baronio M, Sadia H, Paolacci S, et al. Etiopathogenesis of sacroiliitis: implication for assessment and management. Korean J Pain. 2022;33(4):294-304. http://doi.org/10.3344/kjp.2020.33.4.294

Read more: All About Sacroiliitis

Arthritis is a term used to describe a set of conditions that cause joint inflammation and damage. ² Senthelal S, Li J, Ardeshirzadeh S, et al. Arthritis. [Updated 2022 Jun 19]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK518992/

• Most of these conditions fall into one or two categories: degenerative arthritis (such as osteoarthritis, ³ Sen R, Hurley JA. Osteoarthritis. [Updated 2023 Feb 20]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK482326/ ) or inflammatory arthritis (such as rheumatoid arthritis).
• Symptoms of most types of arthritis include dull and persistent pain, that usually has an insidious or gradual onset, stiffness, and swelling in the joint. ² Senthelal S, Li J, Ardeshirzadeh S, et al. Arthritis. [Updated 2022 Jun 19]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK518992/

Does sacroiliitis lead to arthritis?

Sacroiliitis is often associated with certain types of inflammatory arthritis that affect the spine, including ankylosing spondylitis, ⁴ Wenker KJ, Quint JM. Ankylosing Spondylitis. [Updated 2022 Apr 9]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK470173/ psoriatic arthritis, and rheumatoid arthritis. ⁵ Buchanan BK, Varacallo M. Sacroiliitis. [Updated 2022 Sep 4]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK448141/ In these cases, sacroiliitis is considered a symptom of underlying arthritis. ⁵ Buchanan BK, Varacallo M. Sacroiliitis. [Updated 2022 Sep 4]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK448141/

However, sacroiliitis can also occur independently without being linked to another form of arthritis. ⁶ O’Shea FD, Boyle E, Salonen DC et al. Inflammatory and degenerative sacroiliac joint disease in a primary back pain cohort. Back Pain. 2010;62(4):447-454. https://doi.org/10.1002/acr.20168

Common non-arthritic causes of sacroiliitis include ¹ Baronio M, Sadia H, Paolacci S, et al. Etiopathogenesis of sacroiliitis: implication for assessment and management. Korean J Pain. 2022;33(4):294-304. http://doi.org/10.3344/kjp.2020.33.4.294 :

• Macro trauma. A fall or accident that results in trauma to the pelvis or lower back can cause sacroiliitis.
• Micro trauma. Variations in how an individual bends and mechanically navigates their environment can lead to micro-injuries within the sacroiliac ligaments.
• Overuse. Repetitive activities involving the lower back and pelvis, such as long-distance running or cycling, and manual labor involving repetitive twisting can increase pressure on the SI joints.
• Pregnancy. The sacroiliac joint can become strained or inflamed during pregnancy due to increased weight and pressure on the pelvis, causing pain.

• Gait abnormalities. Abnormalities in how a person walks or stands can place extra stress on the SI joint(s) and cause inflammation. Long strides in a gait cycle can irritate the sacroiliac joints. The most common cause of gait abnormalities is leg length discrepancy.
• Infection. In rare cases, a bacterial or viral infection can cause sacroiliitis.

Prolonged inflammation of the SI joint can cause damage to the joint over time, which can increase the risk of developing arthritis.

It’s important to note that not all cases of sacroiliitis lead to arthritis, and the development of arthritis can vary from person to person. ⁶ O’Shea FD, Boyle E, Salonen DC et al. Inflammatory and degenerative sacroiliac joint disease in a primary back pain cohort. Back Pain. 2010;62(4):447-454. https://doi.org/10.1002/acr.20168 Early diagnosis and treatment of sacroiliitis can help prevent or slow down the development of arthritis.

If you experience symptoms of sacroiliitis or arthritis, it is important to speak with a physician trained in diagnosing and treating musculoskeletal pain, who can help determine the underlying cause of your symptoms and develop a treatment plan that is right for you.

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