Osteitis Condensans ilii-MRI

32 years multiparous lady with complaints of pain SI joints location ( left > right ) with pain involving the hip joint as well with clinically positive compression test for SI joints. MR shows diffuse pyriform areas of low signal intensity  juxta articular lesions involving both iliac bones symmetrically in the lower 2/3^rd with focal fatty marrow changes of the juxta articular sacral alae, with no widening, asymmetry, destruction, marrow edema, soft tissue collection. The features are highly suggestive of Osteitis Condensans ilii

Case by Dr MGK Murthy, MD, DNB

Teaching points:

1. It is predominantly found in women usually after child births.
2. It is often seen in young people, bilaterally and symmetrically with  general prevalence of 1.6 to 3 percent.
3. Sacral involvement is not noted.
4. Unilateral types are uncommon but noted.
5. The etiology is possibly due to laxity of the ligaments in pregnancy, leading to subtle malalignments and fibrous tissue proliferation with stress response with increase osteoblastic activity with some authers suggesting increase density of trabeculations.
6. Clinically the compression test for  sacro-iliac tenderness is likely to be positive amongst few people. However not associated chronic back pain or disability.
7. Marrow edema / Radiological malalignment / destruction / soft tissue collection is most uncommon.
8. All the other varieties of sacro-ilitis particularly the ankylosing spondylitis would show some marrow edema, ill definition and subchondral erosions.
9. Chest X-ray, serological evaluation particularly with reference to HLAB27, X-ray / CT sacro-iliac joints along with contrast MRI and if needed bone scan would play useful role.