Radiograph plays a key role in the diagnosis of osteoarthritis, but lacks sensitivity for the diagnosis of early arthritis. This is extremely important because this reduced sensitivity has no -- or extremely limited -- clinical impact due to the lack of treatments with proven efficacy, according to a presentation here at the European Society of Radiology's 2^nd European Congress of Radiology (ESR).

"Degenerative joint disease probably starts around the 20s or 30s and is arthritis by the age of 80, so it takes 60 years," said Bruno C. Vande Berg, MD, PhD, department of radiology, Saint Luc University Clinics, Université Catholique de Louvain, Brussels, Belgium. "In fact, a single surgeon will not be able to assess the value of his treatment because he will need to wait 30 or 40 years to be sure that the intervention will affect the natural history of the osteoarthritis".

According to the presentation, cartilage loss in hip osteoarthritis generally develops focally and slowly. On radiographs, focal joint space narrowing generally occurs in the superolateral or posteroinferior or superomedial poles of the joint, with subchondral erosions and marginal osteophytes as secondary findings. In hip osteoarthritis, the femoral pads may migrate in three different directions in the coronal plate. Most frequently, cartilage loss occurs in the upper joint space.

Conventional magnetic resonance (MR) imaging is more effective for displaying changes to the secondary osseous and soft tissue (capsule, synovium and labrum) than to cartilage, Dr. Vande Berg said. Plain radiographs are not sensitive, he said, but there are few other options.

"[Computed tomography] or MR arthrography provides a better evaluation of these changes but should only be performed in cases where conservative surgery offers a significant clinical improvement for the patient," he explained.

"In rapidly destructive osteoarthritis, cartilage loss occurs rapidly and is more global. Rapidly destructive arthritis is a disease where total loss of joint space occurs in less than 1 year. There is a lack of osteocytes, it is rapidly occurring and there is no margin erosion," Dr. Vande Berg said. "There is joint space narrowing, then fragmentation, collapse and necrosis. All this occurs in contact areas. So this is a disease of the cartilage that occurs extremely rapidly. It occurs mostly in elderly patients. We rarely see it in patients around 40 or 50. While radiographs remain normal at the onset, MR imaging may show extensive synovium and osseous changes that can cause confusion with osteonecrosis or infection".

"We may keep in mind that MRI imaging of the hip cartilage has limited sensitivity and really a take home message is to look at the MR image with the corresponding radiograph," Dr. Vande Berg said.