Effusion detected by ultrasonography and overweight may predict the risk of knee osteoarthritis in females with early knee osteoarthritis: a retrospective analysis of Iwaki cohort data

Background Knee osteoarthritis (OA) has enormous medical and socioeconomic burdens, which early diagnosis and intervention can reduce. We investigated the influence of knee effusion on the progression of knee OA in patients with early knee OA. Methods A total of 404 participants without radiographic knee OA were assessed from a 3-year longitudinal analysis. Participants were classified into non-OA and early knee OA groups. The effusion area (mm 2 ) was quantified using ultrasonography. Receiver operating characteristic and logistic regression analyses were performed. Results At the 3-year follow-up, 114 of 349 knees (32%) had progressed from non-OA and 32 of 55 knees (58%) had progressed from early knee OA to radiographic knee OA. Logistic regression analysis showed that female sex (odds ratio [OR] 3.36, 95% confidence interval [CIs] 2.98–5.42), early knee OA (OR 2.02, 95% CI 1.08–3.75), body mass index (OR 1.11, 95% CI 1.02–1.19), and effusion area (OR 1.01, 95% CI 1.01–1.02) were significantly correlated with knee OA progression. Women who were overweight (body mass index ≥ 25 kg/m 2 ) with more severe effusion had a higher risk of OA progression (area under the curve = 0.691, OR = 6.00) compared to those not overweight (area under the curve = 0.568, OR = 1.91). Conclusion Knee effusion may be an indicator of the progression of early-stage knee OA.