Prevalence and development of hip and knee osteoarthritis according to American College of Rheumatology criteria in the CHECK cohort

Background: We aimed to evaluate the prevalence of hip and knee osteoarthritis (HOA and KOA) according to American College of Rheumatology (ACR) criteria among participants with suspected early symptomatic osteoarthritis (OA) in the CHECK cohort. We also assessed whether participants not fulfilling ACR criteria at baseline develop ACR-defined OA at 2-year and/or 5-year follow up, and which baseline factors are associated with this development.
Methods: The CHECK cohort included 1002 subjects with first presentation of knee and/or hip complaints. The primary outcome was onset of HOA and/or KOA according to the ACR criteria, including the clinical classification criteria and the combined clinical and radiographic classification criteria at 2-year and/or 5-year follow up.
Results: Of the participants with hip complaints, 63% (n = 370) were classified as having HOA at baseline according to the ACR criteria. Of those not classified with HOA at baseline, 40% developed HOA according to the clinical or combined clinical/radiographic ACR criteria after 2 and/or 5 years. Up to 92% of participants (n = 829) with knee complaints were classified as having KOA at baseline; of those not classified with KOA at baseline, 55% developed KOA according to the clinical ACR criteria or the clinical/radiographic ACR criteria after 2 and/or 5 years. The following factors were associated with development of HOA: morning stiffness (OR 2.39; 95% CI 1.14-4.98), painful internal rotation (OR 2.53; 95% CI 1.23-5.19), hip flexion < 115° (OR 2.33; 95% CI 1.17-4.64) and erythrocyte sedimentation rate (ESR) < 20 mm/h (OR 2.94; 95% CI 1.13-7.61). No variables were associated with development of KOA at 2-year and/or 5-year follow up.
Conclusions: A large proportion of persons with hip complaints not fulfilling the ACR criteria at baseline develop HOA after 2 and/or 5 years of follow up. Almost all persons with knee complaints already fulfill the clinical and/or radiographic ACR criteria for OA, and half of the persons not fulfilling criteria at baseline will do so after 5 years of follow up. Several individual ACR criteria for HOA at baseline were associated with the development of HOA at follow up. This association was not proven for KOA, probably because of the small number of subjects developing KOA in this study.