Sacroiliitis
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Sacroiliitis is an inflammation of the sacroiliac joint. Inflammation may occur in the region of the sacroiliac joint. This joint is relatively inflexible and connects the sacrum to the pelvis. It is associated with a variety of infectious or inflammatory conditions. Pain occurs either unilaterally or bilaterally in the low back, buttock and upper leg.
Risk Factors for Sacroiliitis
- A history of bone, joint or skin infections. Some people are more prone to infections, and an infection is one possible cause of sacroiliitis.
- Injury or trauma to your spine, pelvis or buttocks. Torn ligaments or trauma may create inflammation or infection of the sacroiliac joints.
- Urinary tract infection. This infection may spread from your urinary tract, which includes your kidneys, bladder and urethra, to your sacroiliac joints.
- Pregnancy. The pelvic bone's expansion to prepare for childbirth may inflame the area around your sacroiliac joints.
- Endocarditis. This infection of your heart's inner lining may spread to your sacroiliac joints.
Causes of Sacroiliitis
- Heavy lifting, especially incorrect training or when muscles aren't prepared for the activity
- A traumatic injury or sudden impact, such as a motor vehicle accident or a fall, affecting your spine, lower back, pelvis or buttocks
- Spondyloarthropathies, which include ankylosing spondylitis, arthritis associated with psoriasis and others
- Degenerative arthritis, also called osteoarthritis of the spine, causing degeneration of the sacroiliac joints, which can cause mild inflammation and pain
- Pregnancy, because the pelvis must stretch to accommodate childbirth
- Infection of the sacroiliac joint, sometimes caused by bacteria in food (brucellosis)
Diagnosis
Clinical Features
- Pain and stiffness at lower back, thighs or buttocks, especially in the morning or when sitting for a long period of time
- Pain affecting hips and shoulders
- Pain that worsens with walking because the swinging motion of hips strains sacroiliac joints
- Inflammation in one or both of the eyes (uveitis or iritis)
- Psoriasis, an inflammatory skin condition
- Bloody diarrhea
- A low-grade fever that appears quickly
Physical Examination
- Localized pain that seems to be on or around sacroiliac joints, which can be determined by pressing on sacroiliac region while patient moves in certain ways to gently stress the sacroiliac joint.
Laboratory Diagnosis
- Cultures of fluid from the sacroiliac joint
- Blood culture, if the cause appears to be an infection
- X-rays of sacroiliac joints
- Magnetic resonance imaging (MRI) scan of sacroiliac joints
X-ray Findings in Differential Diagnosis
- Normal SI joint is uniform in size throughout
- Only lower 2/3 of SI joint are true joint
- Earliest sign of sacroiliitis is widening of the joint
- Sclerosis and narrowing represent healing
- Unilateral Sacroiliitis
- TB
- Bilateral and symmetric
- Ankylosing spondylitis
- Narrowing and sclerosis
- Fusion eventually
- Almost always bilateral
- Inflammatory bowel disease
- Ulcerative colitis more often then Crohn’s
- Ankylosing spondylitis
- Enteropathic arthritis more common in Crohn’s-usually knee
- Inflammatory bowel disease usually does not affect the spine as often as ankylosing spondylitis
- Bilateral and asymmetric
- Rheumatoid arthritis, psoriasis and Reiter’s may affect one SI joint but usually affect both
- Usually asymmetric
- Gout is a rare cause of sacroiliitis
- May see erosions in spine
- SI Disease in Crohn’s
- About 3-16% of patient with Crohn’s
- Occurs independent of activity of bowel disease
- HLA B27 antigen is usually elevated
- Bilateral SI joint narrowing and erosions with sclerosis
- Identical appearance to AS
- SI Disease in Ulcerative Colitis
- About 1-22% of patients with UC
- Not correlated with activity of bowel disease
- Spondylitis usually precedes onset of bowel findings
- Appears identical to AS
- More common in males
- Peripheral joint involvement in 50-70%
- Especially shoulders and hips
- Higher incidence of elevated HLA B27 in patients with spondylitis or iritis
Differential Diagnosis of Causes of Sacroiliitis
- Bilateral & symmetrical
- Ankylosing spondylitis
- Reiter's syndrome
- Enteropathic
- Bilateral & assymetrical
- Unilateral
- Gout
- Infection
- Osteoarthritis