Sacroiliitis x ray

• 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

• 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

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