The sacroiliac joints link your pelvis and lower spine. They're made up of the sacrum — the bony structure above your tailbone and below your lower vertebrae — and the top part (ilium) of your pelvis. There are sacroiliac joints in both the right and left sides of your lower back. Strong ligaments hold these joints in place. The sacroiliac joints support the weight of your upper body when you stand.
Sacroiliitis (say-kroe-il-e-I-tis) is an inflammation of one or both of your sacroiliac joints — situated where your lower spine and pelvis connect. Sacroiliitis can cause pain in your buttocks or lower back, and can extend down one or both legs. Prolonged standing or stair climbing can worsen the pain.
Sacroiliitis can be difficult to diagnose, because it can be mistaken for other causes of low back pain. It's been linked to a group of diseases that cause inflammatory arthritis of the spine. Treatment might involve physical therapy and medications.
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The pain associated with sacroiliitis most commonly occurs in the buttocks and lower back. It can also affect the legs, groin and even the feet. Sacroiliitis pain can be aggravated by:
- Prolonged standing
- Bearing more weight on one leg than the other
- Stair climbing
- Taking large strides
Causes for sacroiliac joint dysfunction include:
- Traumatic injury. A sudden impact, such as a motor vehicle accident or a fall, can damage your sacroiliac joints.
- Arthritis. Wear-and-tear arthritis (osteoarthritis) can occur in sacroiliac joints, as can ankylosing spondylitis — a type of inflammatory arthritis that affects the spine.
- Pregnancy. The sacroiliac joints must loosen and stretch to accommodate childbirth. The added weight and altered gait during pregnancy can cause additional stress on these joints and can lead to abnormal wear.
- Infection. In rare cases, the sacroiliac joint can become infected.
As with other conditions that cause chronic pain, sacroiliitis can result in depression and insomnia.
April 22, 2021
- Frontera WR. Sacroiliac joint dysfunction. In: Essentials of Physical Medicine and Rehabilitation: Musculoskeletal Disorders, Pain, and Rehabilitation. 3rd ed. Philadelphia, Pa.: Saunders Elsevier; 2015. http://www.clinicalkey.com. Accessed Oct. 23, 2015.
- Wu DT, et al. Diagnosis and differential diagnosis of ankylosing spondylitis and non-radiographic axial spondyloarthritis in adults. http://www.uptodate.com/home. Accessed Oct. 23, 2015.
- Navallas M, et al. Sacroiliitis associated with axial spondyloarthritis: New concepts and latest trends. RadioGraphics. 2013;33:1.
- FDA Drug Safety Communication: FDA strengthens warning that non-aspirin nonsteroidal anti-inflammatory drugs (NSAIDs) can cause heart attacks or strokes. U.S. Food and Drug Administration. http://www.fda.gov/Drugs/DrugSafety/ucm451800.htm. Accessed Nov. 2, 2015.
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