Osteitis condensans ilii

Osteitis condensans ilii is characterised by benign sclerosis of the ilium adjacent to the sacroiliac (SI) joint, typically bilateral and triangular in shape.

Clinical presentation

It is usually asymptomatic but uncommonly may cause lower back pain, with a frequency about 1-2.5% ⁴.

Pathology

The underlying aetiology is believed to be mechanical stress across the sacroiliac  joint. That it is most often seen in women who have given birth supports this hypothesis, however, women who have not given birth and men can be affected ^2-4. 

Radiographic features

Plain radiograph and CT

Sclerosis of the ilial part of the sacroiliac joint is seen, typically bilateral and triangular in shape ^3-4. Lack of involvement of sacrum or joint space narrowing is considered diagnostic and thus, may obviate the need for further imaging ³. Unilateral disease has also been reported. 

Treatment and prognosis

It carries a benign prognosis and may even resolve spontaneously. 

Differential diagnosis

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.