Magnetic resonance imaging has an increasingly important role in the early detection and diagnosis of osteoarthritis, although for now it remains one of several diagnostic tools that also include x-rays, clinical findings, and lab results.
Physicians who treat patients with osteoarthritis (OA) need further research results to better clarify the best use of MRI in early OA detection, said Dr. Philip Conaghan, professor of musculoskeletal medicine at the University of Leeds (England).
Dr. Philip Conaghan
In June, Dr. Conaghan and his colleagues on the OA Imaging Working Group for the Osteoarthritis Research Society International (OARSI) issued 11 propositions on using MRI to define OA – propositions that the group said need formal testing "regarding their diagnostic performance before they are more widely used" (Osteoarthritis Cartilage 2011;19:963-9).
The working group clearly endorsed MRI, saying that "MRI may add to the diagnosis of OA and should be incorporated into the [American College of Rheumatology] diagnostic criteria," but in the same proposition, the working group also reiterated the role of x-ray, clinical, and laboratory parameters. Other propositions caution that "no single MRI finding is diagnostic of MRI," and that "certain MRI changes in isolation ... are not diagnostic of osteoarthritis."
The working group’s propositions included two MRI-based definitions of OA, for the tibiofemoral form and for the patellofemoral type.
In a recent talk on MRI and OA, Dr. Conaghan stressed the potential that MRI holds for early OA detection.
"We need to develop an early OA culture," similar to what has emerged for rheumatoid arthritis, he said speaking in May at the annual European Congress of Rheumatology in London. "In OA, we need a culture of early intervention" that would rely on early detection, most likely using MRI.
"Clinical features may suffice at present" for early OA detection, but MRI offers the best individualized option for assessing cartilage, bone features, and possibly the meniscus, he said. Soluble biomarkers may be more feasible than MRI, but biomarkers need more development and for early detection are "not there yet."
The sheer frequency of MRI lesions in OA patients may prove limiting. OA lesions appear more often on MRI than on x-rays. In five different reported series, the prevalence of cartilage defects visible by MRI in OA patients was 85%-98%, and the prevalence of osteophytes was 70%-100%, Dr. Conaghan noted. Often the MRI changes appear with no radiographic change visible. Other MRI changes that look like promising OA markers are bone marrow lesions and bone shape.
The OARSI Working Group defined tibiofemoral OA by MRI as either both items from group A, or one group A item and at least two from group B. The group A diagnostic features are definite osteophyte formation and full-thickness cartilage loss. The group B items are a subchondral bone marrow lesion or cyst that is not associated with meniscal or ligamentous attachments; meniscal subluxation, maceration, or degenerative tear; partial-thickness cartilage loss, and bone attrition.
The working group’s definition of patellofemoral OA requires both a definitive osteophyte and partial- or full-thickness cartilage loss.
Dr. Conaghan said that he had no relevant disclosures.