Differences between OCI and ankylosing spondylitis
| OCI | Ankylosing spondylitis | |
|---|---|---|
| Age | Young adults | Young adults |
| Sex | Common in women | Common in men |
| Presentation | Usually after pregnancy | No specific correlation |
| HLA-B27 | Usually absent | Present in 90% |
| Spine involvement | Absent | Present |
| Sacroiliac joint abnormality | ||
| Distribution | Bilateral, symmetric; iliac | Bilateral, symmetric; iliac > sacrum |
| Osteopenia | Absent | Present |
| Sclerosis | Well defined | Poorly defined |
| Joint space | Normal | Narrowed |
| Erosion | Absent | Commonly seen |
| Bony ankylosis | Absent | Common |