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.
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 congress, 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. Through a multiphase process of discussion and voting, the group agreed on a set of nine propositions and two OA definitions based on MRI criteria. (See boxes.) These constitute “statements of preamble and context setting.” The two definitions “offer an opportunity for formal testing against other diagnostic constructs,” said Dr. Hunter of 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 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.”
An osteoarthritis specialist who was not involved with the working group cautioned that waiting for MRI structural changes that are specific for OA may still miss a truly early diagnosis, before irreversible pathology occurred.
“There are early changes [seen with MRI] that are not picked up on radiographs, but we don't yet have a standardized, validated definition of an earlier stage” on MRI, Dr. Tuhina Neogi, a rheumatologist at Boston University, said in an interview.
Dr. Hunter said that he has received research support from AstraZeneca, DJO Inc. (DonJoy), Eli Lilly & Co., Merck & Co., Pfizer Inc., Stryker Corp., and Wyeth. Eight of the other members of the working group also provided disclosures, whereas the remaining seven members said they had no disclosures. Dr. Neogi had no disclosures.
The OARSI Panel's Propositions
The following are nine propositions on MRI diagnosis 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 and should be incorporated into the ACR diagnostic criteria including x-ray, clinical, and laboratory parameters.
3. MRI may be included in clinical studies according to the criteria detailed above, but should not be a primary diagnostic tool.
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.
Two MRI-Based Definitions
The panel arrived at the following two definitions for MRI findings that were diagnostic of knee osteoarthritis:
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).