Osteitis condensans ilii is characterised by benign sclerosis of the ileum adjacent to the sacroiliac joint. It is typically bilateral and symmetrical, and tends to be triangular in shape. The sacroiliac joint is not involved. It is most commonly seen in multiparous females, however the condition is by no means restricted to multiparous females 2.
The underlying aetiology is believed to be mechanical stress across the SI joint.
It is usually asymptomatic but uncommonly may cause lower back pain.
Plain film and CT
Sclerosis of the ilial part of sacroiliac joint is seen. Sacrum is not involved.
The main differential diagnosis is a sacroiliitis, but with osteitis condensans ilii the SI joint is normal with no irregularity, erosions or loss of joint space.