6. Causes of sacroiliitis - symmetric vs asymmetric (mnemonic)
PAIR
Mnemonic
P: psoriatic arthritis
A: ankylosing spondylitis
I: inflammatory bowel disease related
R: reactive (e.g. Reiter syndrome)
P & R (letters are far apart) are the asymmetric causes and the inside
letters A & I (letters are close together) are the symmetric causes.
7. Sacroiliitis grading (New York criteria)
Sacroiliitis grading can be achieved using plain radiographs according to
the New York criteria.
1. Grade 0: normal
2. Grade I: some blurring of the joint margins - suspicious
3. Grade II: minimal sclerosis with some erosion
4. Grade III
• definite sclerosis on both sides of joint
• severe erosions with widening of joint space with or without
ankylosis
5. Grade IV: complete ankylosis
11. Grade 1 (a) sacroiliitis was defined as focal erosions seen on
only one of either semicoronal or axial images.
Grade 2 (b) sacroiliitis was defined as erosions seen on 25 %
of consecutive semicoronal or axial images.
Grade 3 (c, d) sacroiliitis included bony erosions on C25 % of
consecutive semicoronal or axial images, or joint space
alteration, or partial ankylosis