BRUSSELS – The use of magnetic resonance imaging may enable earlier recognition of knee osteoarthritis, and should be incorporated into recommended diagnostic criteria, a panel of 16 osteoarthritis experts concluded.
Using MRI to define knee osteoarthritis (OA) may allow detection of the disease before radiographic changes occur. But despite a growing body of literature on the role of MRI in OA, little uniformity exists for its diagnostic application, perhaps because of the absence of criteria for an MRI-based structural diagnosis of OA, the group said.
Dr. Tuhina Neogi
The Osteoarthritis Research Society International (OARSI) organized the 16-member panel, the OA Imaging Working Group, to develop an MRI-based definition of structural OA. The working group sought to identify structural changes on MRI that defined a structural diagnosis of knee OA, Dr. David J. Hunter and the other members of the working group wrote in a poster presented at the World Congress on Osteoarthritis, which was organized by OARSI.
The working group began with a literature review through April 2009, a process that yielded 25 studies that met the group’s inclusion criteria and evaluated MRI diagnostic performance. The 16 members also contributed candidate propositions dealing with key aspects of MRI diagnosis of knee OA.
Through a multiphase process of discussion and voting, the group agreed on the following set of nine propositions based on MRI criteria of knee OA:
1. MRI changes of OA may occur in the absence of radiographic findings of OA.
2. MRI may add to the diagnosis of OA and should be incorporated into the ACR diagnostic criteria including x-ray, clinical, and laboratory parameters.
3. MRI may be used for inclusion in clinical studies according to the criteria detailed above, but should not be a primary diagnostic tool in a clinical setting.
4. Certain MRI changes that occur in isolation are not diagnostic of OA. These include cartilage loss, change in cartilage composition, cystic change and development of bone marrow lesions, ligamentous and tendinous damage, meniscal damage, and effusion and synovitis.
5. No single finding is diagnostic of knee OA.
6. MRI findings indicative of knee OA may include abnormalities in all tissues of the joint (bone, cartilage, meniscus, synovium, ligament, and capsule).
7. Given the multiple tissue abnormalities detected by MRI in OA, diagnostic criteria are likely to involve several possible combinations of features.
8. Definite osteophyte production is indicative of OA.
9. Joint space narrowing as assessed by (nonweight bearing) MRI cannot be used as a diagnostic criterion.
Similarly, the working group agreed on the following two definitions for MRI findings that were diagnostic of knee OA:
1. Tibiofemoral OA should have either both features from group A (below), or one feature from group A and at least two features from group B. Examination of the patient must also rule out joint trauma within the last 6 months (by history) as well as inflammatory arthritis (diagnosed by radiographs, history, and laboratory findings).
• Group A features: Definite osteophyte formation; full thickness cartilage loss.
• Group B features: Subchondral bone marrow lesion or cyst not associated with meniscal or ligamentous attachments; meniscal subluxation, maceration, or degenerative (horizontal) tear; partial-thickness cartilage loss (without full thickness loss).
2. Patellofemoral OA requires both of the following features involving the patella or the anterior femur or both:
• Definite osteophyte formation.
• Partial- or full-thickness cartilage loss.
These constitute “statements of preamble and context setting.” The two definitions “offer an opportunity for formal testing against other diagnostic constructs,” said Dr. Hunter, a rheumatologist and professor of medicine at the University of Sydney and his associates in the working group.
The working group noted that the American College of Rheumatology in 1986 first released the current standard criteria for diagnosing OA, which deal only with radiographic imaging (Arthritis Rheum. 1986;29:1039-49). The European League Against Rheumatism published more current recommendations this year, but focused on a clinical diagnosis that did not involve imaging (Ann. Rheum. Dis. 2010;69:483-9).
The working group aimed to “include MRI as a means to define the disease with the intent that one may be able to identify early, pre-radiographic disease, thus enabling recruitment of study populations where structure modification (or structure maintenance) may be realistic in a more preventive manner.”
The group cautioned that prior to using the definitions, “it is important that their validity and diagnostic performance be adequately tested.” They also stressed that “the propositions have been developed for structural OA, not for a clinical diagnosis, not for early OA, and not to facilitate staging of the disease.” The propositions “are not to detract from, nor to discourage the use of traditional means for diagnosing OA.”