Summary of radiological differences reported by McEwen et al6
| Feature | Ankylosing spondylitis and spondylitis of ulcerative colitis and regional enteritis | Spondylitis associated with psoriasis and reactive arthritis |
|---|---|---|
| Sacroiliitis | Severe and symmetrical | Sacroiliitis sometimes unilateral or bilaterally asymmetrical |
| Symphisitis | More frequent | Less frequent |
| Osteoporosis | More frequent | Less frequent |
| Lumbar straightening | More frequent | Less frequent |
| Apophyseal joint involvement | More frequent | Less frequent |
| Squaring | More frequent | Less frequent |
| Syndesmophytes | More frequent, usually symmetrical | Less frequent, usually asymmetrical |
| Shape and size of syndesmophytes | Marginal (see text) | Usually “other than marginal” (see text) |
| Ligamentous ossification | More frequent | Less frequent |
| Progression of syndesmophytes | Lumbar to dorsal to cervical | Random progression |