Ultrasonographic imaging for early-stage knee osteoarthritis: Radiographic and clinical associations in a cross-sectional single-center study

Objective: To evaluate whether ultrasonography (US) detects early-stage knee osteoarthritis (OA) more effectively than conventional radiography (CR) in a population representing primary and occupational healthcare, and to assess associations between imaging findings and symptoms. Design: In this cross-sectional study, 315 subjects (60% women; mean age 49 years, range 21-63 years) with knee symptoms underwent knee US and CR, resulting in assessment of 345 knees. Ultrasonographic evaluation included effusion, synovial hypertrophy, osteophytes, femoral cartilage damage, meniscal pathology, and protrusion, from which a composite US sum score was constructed. Radiographic severity was graded using the Kellgren-Lawrence (KL) scale (grade 0, n = 128; grade 1, n = 90; grade 2, n = 78; grade 3, n = 38; grade 4, n = 11). WOMAC questionnaires were completed prior to imaging. Statistical analyses included Kruskal-Wallis and Mann-Whitney tests, univariate analyses, and Pearson correlation coefficients. Results: US detected more osteophytes than CR, particularly at the femoral margins, while tibial osteophyte detection was comparable between modalities. US identified more femoral cartilage damage than CR-detected joint-space narrowing. Meniscal protrusion was associated with radiographic joint-space narrowing and KL grade (p < 0.001). Effusion size and synovial hypertrophy increased with higher KL grades (p < 0.001). The US sum score correlated with KL grade (r = 0.73, p < 0.001). Both the US sum score and KL grade showed modest associations with WOMAC scores. Conclusions: US detects more structural abnormalities than CR in early-stage knee OA. While ultrasonographic findings correlate with radiographic severity, their associations with clinical symptoms remain limited, supporting US as a complementary tool for structural assessment in knee OA.