Table 2

 Differences between OCI and ankylosing spondylitis

OCIAnkylosing spondylitis
AgeYoung adultsYoung adults
SexCommon in womenCommon in men
PresentationUsually after pregnancyNo specific correlation
HLA-B27Usually absentPresent in 90%
Spine involvementAbsentPresent
Sacroiliac joint abnormality
    DistributionBilateral, symmetric; iliacBilateral, symmetric; iliac > sacrum
    OsteopeniaAbsentPresent
    SclerosisWell definedPoorly defined
    Joint spaceNormalNarrowed
    ErosionAbsentCommonly seen
    Bony ankylosisAbsentCommon