Osteitis condensans ilii or sacro-iliitis?

Eight patients with a radiological diagnosis of Osteitis condensans ilii (OCI) had clinical features similar to those of 8 patients with sacro-iliitis (SI). The X-ray appearances may be very difficult to differentiate on standard films and discrimination between the two conditions has to be made from a combination of clinical and radiological findings. The term OCI should be regarded with suspicion when applied to young people with a history of backache.