The challenge of the definition of early symptomatic knee osteoarthritis: a proposal of criteria and red flags from an international initiative promoted by the Italian Society for Rheumatology

The aim of this study was to establish consensus for potential early symptomatic knee osteoarthritis (ESKOA) clinical definition and referral criteria from primary care to rheumatologists, based on available data from literature and a qualitative approach, in order to perform studies on patients fulfilling such criteria and to validate the obtained ESKOA definition. A complex methodological approach was followed including: (1) three focus groups (FG), including expert clinicians, researchers and patients; (2) a systematic literature review (SLR); (3) two discussion groups followed by a Delphi survey. FG and SLR were performed in parallel to inform discussion groups in order to identify relevant constructs to be included in the modified Delphi survey. ESKOA is defined in the presence of: (a) two mandatory symptoms (knee pain in the absence of any recent trauma or injury and very short joint stiffness, lasting for less than 10 min, when starting movement) even in the absence of risk factors, or (b) knee pain, and 1 or 2 risk factors or (c) three or more risk factors in the presence of at least one mandatory symptom, with symptoms lasting less than 6 months. These criteria are applicable in the absence of active inflammatory arthritis, generalized pain, Kellgren-Lawrence grade >0, any recent knee trauma or injury, and age lower than 40 years. Knee pain in the absence of any recent trauma lasting for less than 6 months was considered as the referral criterion to the rheumatologist for the suspicion of ESKOA. This consensus process has identified provisional clinical definition of ESKOA and defined potential referral criterion to rheumatologist, in order to test ESKOA obtained definition in prospective validation studies.