Unilateral Accessory Sacroiliac Joint with Bone Marrow Edema Mimicking Sacroiliitis.

Accessory sacroiliac joint (SIJ) is described as a common anatomical variant, identified in 13–18% and up to 40% of the general population1,2. It can be unilateral or bilateral and is related to aging, obesity, or women with multiple deliveries2,3. The patient, a 53-year-old white woman, presented with low back pain and left buttock pain for 6 months. She had no fever and local pressure on left SIJ reproduced …