Table 1

Summary of radiological differences reported by McEwen et al6

FeatureAnkylosing spondylitis and spondylitis of ulcerative colitis and regional enteritisSpondylitis associated with psoriasis and reactive arthritis
SacroiliitisSevere and symmetricalSacroiliitis sometimes unilateral or bilaterally asymmetrical
SymphisitisMore frequentLess frequent
OsteoporosisMore frequentLess frequent
Lumbar straighteningMore frequentLess frequent
Apophyseal joint involvementMore frequentLess frequent
SquaringMore frequentLess frequent
SyndesmophytesMore frequent, usually symmetricalLess frequent, usually asymmetrical
Shape and size of syndesmophytesMarginal (see text)Usually “other than marginal” (see text)
Ligamentous ossificationMore frequentLess frequent
Progression of syndesmophytesLumbar to dorsal to cervicalRandom progression