A confident diagnosis of knee osteoarthritis can be made without radiographic examination in adults older than 40 years based on criteria described in evidence-based recommendations to be published by the European League Against Rheumatism.
The criteria include usage-related knee pain, short-lived morning stiffness, functional limitation, and one or more “typical” examination findings, such as crepitus, restricted movement, and bony enlargement.
Clinical signs, symptoms, risk factors, and plain radiography are the cornerstones of the recommendations, which focus specifically on clinical diagnosis vs. classification, distinguishing them from the American College of Rheumatology criteria, said Weiya Zhang, Ph.D., of the University of Nottingham (England), lead author of the recommendations, which were presented at the annual European Congress of Rheumatology in Copenhagen and are slated for publication in upcoming issue of the Annals of Rheumatic Disease.
The recommendations were developed by a EULAR task force of 17 osteoarthritis experts from 12 European countries, explained Dr. Zhang.
A systematic literature search was undertaken to identify the best available research evidence to support the various propositions; the strength of recommendation for each diagnostic consideration was based on research evidence and clinical expertise, according to Dr. Zhang. The diagnostic accuracy of the recommendations was tested using multiple predictive models in two populations, including one each from the Netherlands and the United Kingdom, he explained.
Among the recommendations, risk factors emerged as an important consideration for identifying patients with knee pain in whom knee OA is the most likely diagnosis, Dr. Zhang and his colleagues determined. The risk factors that are strongly associated with the incidence of knee OA include increasing age older than 50 years, female sex, higher body mass index, previous knee injury or malalignment, joint laxity, occupational or recreational usage, family history, and the presence of Heberden's nodes, they wrote.
The EULAR task force also determined that plain radiography of the knee (including a weight-bearing, a semiflexed, and lateral and skyline views) continues to be the clinical standard imaging modality for morphologic assessment of knee OA, but noted that it is an adjunct rather than a central feature for diagnostic purposes. They also observed that other imaging modalities, such as MRI, sonography, and scintigraphy, are “seldom indicated for diagnosis of OA,” according to the recommendations. Classic radiographic features “are focal joint space narrowing, osteophyte, subchondral bone sclerosis, and subchondral cysts.”
Other recommendations cover the definition of knee OA, OA subsets, typical symptoms and signs, the use of laboratory tests, and differential diagnosis.
The authors acknowledged that the recommendations are limited because they were derived from literature based on different studies.
Dr. Zhang reported having no relevant financial relationships to disclose.
EULAR considers x-rays unnecessary in patients older than 40 years of age.
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