Figure 5. Tuberculous sacroiliac joint septic arthritis. (a) This patient presented with right buttock pain and sciatica. Note widening of the right sacroiliac (SI) joint (arrows). (b,c) CT confirms SI joint widening and demonstrates extensive abscess formation deep to the psoas and in the erector spinae and gluteus muscles. Note also the soft tissue thickening and oedema in the right sciatic notch (curved arrow). Axial (d)and coronal (e) STIR images show fluid within the right SI joint as well as bone marrow oedema in the adjacent sacrum and iliac bone. There is also extensive oedema in the gluteal muscles and subcutaneous fat.
