Prevalence of Knee Radiographic Symptomatic Osteoarthritis and Ultrasound Features Across Sex and Body Mass Index Groups: The Johnston County Health Study.

OBJECTIVE: To quantify general population prevalence, and differences by sex and BMI, in ultrasound (US) features of knee osteoarthritis (KOA), patient-reported knee symptoms (Ksx), radiographic KOA (rKOA), and symptomatic KOA (sxKOA). METHODS: Participants from the Johnston County Health Study (2019-2024; n=902) provided demographic, clinical, and imaging data. Ksx was defined as self-reported pain, aching or stiffness on most days of any one month in the past 12 months. rKOA was defined as Kellgren-Lawrence grade ≥2 (or total knee replacement (TKR)), severe rKOA as grades 3-4 (or TKR), and sxKOA as rKOA and Ksx in the same knee. Standardized US scoring was performed as previously reported. Weighted prevalence estimates and 95% confidence intervals (CI) for Ksx, rKOA, sxKOA, severe rKOA, and US features were calculated overall and by sex and BMI category. RESULTS: Among 902 participants (67% female; 66% non-Hispanic white, mean age 55 years, and BMI 33 kg/m²), the weighted prevalence of Ksx, rKOA, sxKOA, and severe rKOA were 61%, 36%, 27%, and 21%, respectively, all higher (based on non-overlapping CIs) than baseline estimates from the Johnston County Osteoarthritis Project and other cohorts. Ksx, rKOA, sxKOA, and severe rKOA were higher among females and those with obesity. Compared to females with obesity, those with severe obesity had higher prevalence of all radiographic outcomes at moderate and severe grades with non-overlapping CI. US effusion and synovitis were more prevalent in males, whereas medial and lateral cartilage damage were more common in females. With increasing obesity, osteophytes and medial cartilage damage were more prevalent, while gryescale effusion was actually less frequent. CONCLUSION: KOA prevalence continues to increase in the population. Sex and BMI differences in KOA prevalence and US features were most pronounced among females with severe obesity. Distinguishing between sexes and by obesity levels may improve understanding of KOA mechanisms and guide tailored prevention and treatment strategies.