Material and Method: A population-based survey was undertaken in Songkhla, a province in the southern part of Thailand. Residents aged 40 years and older were sampled using primary care units as a primary sampling frame, stratified by age and sex. All participants were taken to a private clinic for an interview and radiographic examination, including anteriorposterior, lateral and skyline views of both knees. Types and severities of involvement in each compartment were graded by one musculoskeletal radiologist.

Results: Of the eligible 694 subjects, 576 (81.4%) agreed to participate in the present study. The prevalence of radiographic patellofemoral osteoarthritis was 37.9%, of which 96% was bilateral involvement. Isolated patellofemoral osteoarthritis was the most common pattern in males (18.0%), while the combined pattern (involvement of both tibiofemoral and patellofemoral compartments) was the most common pattern in females (31.2%). Elderly (OR = 8.8, 95% CI: 5.1-15.3) and obese (OR = 7.9, 95% CI: 3.3-15.3) were independent risk factors predicting patellofemoral osteoarthritis.

Conclusion: There was a high prevalence of patellofemoral osteoarthritis among Thais over 40 years of age, associated with age and obesity.

Keywords: Epidemiology, Risk factors, Patellofemoral osteoarthritis