Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at August 4, 2016

Sacroiliitis, pronounced "say-kroh-il-eee-I-tis," is the medical name for inflammation of one or both of the joints that serve to connect the pelvis to the spine


Definition & Facts 

Sacroiliitis is estimated to affect between 0.2 and 1 percent of adult males and females. The condition's frequent misdiagnosis has hampered research into its exact causes. The sacroiliac joint (SI joint for short) is the largest joint system in the human body. Sometimes sacroiliitis is called sacroiliac joint dysfunction instead. However, the two conditions actually have some differences as noted here:

  • Sacroiliitis. Here, there is inflammation in the SI joint area which may be related to abnormal joint mobility or may be caused by disease or infection.
  • Sacroiliac joint dysfunction. This condition describes structural and functional problems of the joint that may or may not involve inflammation.

Symptoms & Complaints

The chief symptom and complaint of sacroiliitis is pain - constant, chronic pain. The pain often begins in the lower back area and extends into the area of the buttocks and/or lower legs as well.

Depending on whether the SI joint itself is part of the problem, there may be pain in the front or back of the legs or numbness as well. Other common symptoms and complaints in addition to pain include these:

  • Fever
  • Stiffness, especially after a long period of rest.
  • Worsening pain when sitting or when rolling over onto one's side in bed

With severe sacroiliitis, the pain and/or numbness can also extend down into the feet as well as into the groin and inner thigh area. 


There is no one single trigger for sacroiliitis. To the contrary, a variety of activities or conditions may serve as a cause.  Some of the most common causes of sacroiliitis include:

  • Standing for long periods of time.
  • Bearing weight unevenly between legs while standing.
  • Taking long strides while walking or running.
  • Climbing stairs.
  • Running or jogging. In these cases, sacroilitis is a type of sports injury.

In addition, there are a number of conditions known to trigger sacroiliitis or sacroiliac joint dysfunction:

  • Existing arthritis. In particular, degenerative forms of arthritis can compromise the SI joint. 
  • Crohn's disease, lupus, psoriasis, ulcerative colitis, inflammatory bowel disease have all been implicated in the possible development of sacroiliitis.
  • Pregnancy. Pregnancy causes a woman's pelvis and hips to expand to accommodate the growing fetus, and this can cause inflammation and pain in the area of the SI joint as well.
  • Infection. An example would be an untreated urinary tract infection (UTI) that extends into the SI joint area or osteomyelitis, a relatively rare vertebral infection.
  • A trauma to the SI joint area. Car accidents, surgery in or near the pelvic area or a fall can all be examples of trauma that could cause sacroiliitis.

Diagnosis & Tests

Diagnosing sacroiliitis begins with a physical examination. The physician may touch different areas near and around the pelvis (palpation) and take a medical history to look for co-occurring conditions.

The doctor may also order an X-ray or magnetic resonance imaging (MRI) test to take a closer look at the structure and function of the vertebrae, pelvis, and the SI joint. One test that is considered definitive for diagnosing sacroiliitis is to numb a small portion of skin and inject anesthetic into the SI joint area. If the pain ceases suddenly, this is considered a definitive diagnosis.

Treatment & Therapy

Once diagnosis is confirmed there are a range of treatment options that can be used to alleviate the pain and discomfort of sacroiliitis. Some of the most common medicines prescribed include:

  • Pain medications. For slight pain, over-the-counter medications like acetominophen and ibuprofen may be sufficient. In more severe cases, the doctor may order prescription pain relievers.
  • Muscle relaxing medications. Muscle relaxants help ease spasming muscles in the SI joint area, which can also relieve pain.
  • TNF medications (tumor necrosis factor inhibitors). If the underlying cause of sacroiliitis is determined to be ankylosing spondylitis, a condition where the spinal vertebrae begin to spontaneously fuse together due to progressive inflammation, TNF medications may ease the pain as well as the inflammation.
  • Corticosteroids. Injections of corticosteroids can reduce inflammation and thus pain.

Common therapeutic or surgical treatments include the following:

Prevention & Prophylaxis

For sacroiliitis caused by an underlying inflammatory or arthritic condition, the only possible way to prevent sacroiliitis is to strive for the earliest possible diagnosis and treatment so the condition will not become permanent. 

For trauma-related sacroiliitis, there is no guaranteed method of prevention for the trauma itself, but individuals can be careful to avoid accidents or falls to reduce their risk. Women who are pregnant can reduce their risk of developing sacroiliitis by keeping their back muscles and leg muscles strong.