High prevalence of patellofemoral osteoarthritis in China: a multi-center population-based osteoarthritis study.

Background: To describe the prevalence and risk factors of patellofemoral osteoarthritis (PFOA) among Chinese residents.

Methods: A multi-center population-based osteoarthritis study was conducted in 2014. Residents aged ≥ 50 years old were recruited using a cluster sampling method. Subjects completed a home interview and physical examination and had skyline view of radiographs at patellofemoral (PF) joints. Radiographs were read by two trained musculoskeletal researchers, and discordance of a subject's PFOA status between two readers was adjudicated with a third musculoskeletal researcher present. Radiographic OA at PF joint was defined if osteophytes (OST) score was ≥ 2 or if joint space narrowing (JSN) score was ≥ 2 with concurrent grade 1 OST in the PF joint.

Results: Of 3446 subjects (63.0% women) included in this analysis, the prevalence of radiographic PFOA was 23.9% (20.5% men vs. 25.8% women). Prevalence of lateral radiographic OA was higher than medial radiographic OA at PF joint. Grades of both osteophytes and joint space narrowing in the lateral patellofemoral compartment were higher than those in the medial patellofemoral compartment (all P values < 0.001). Women, older age, higher BMI, and fewer years of education were significantly associated with higher prevalence of radiographic PFOA, osteophytes, and joint space narrowing.

Conclusion: Prevalence of radiographic PFOA was high among Chinese population. Key Points • The multi-center population-based osteoarthritis study shows the prevalence of radiographic PFOA was high among Chinese population. • Older age, female gender, obesity, and few years of education were associated with a high risk of PFOA. • Prevalence of lateral radiographic OA was higher than medial radiographic OA at PF joint.