The prevalence of symptomatic knee osteoarthritis (KOA) in Singapore is unknown. We aimed to: (i) validate questionnaires to screen for symptomatic KOA; and (ii) estimate the prevalence of symptomatic KOA in Singapore using the validated algorithms.
Subjects aged ≥50 years were evaluated for symptomatic KOA based on American College of Rheumatology clinical and radiographic criteria in a rheumatology clinic, and completed three sets of adapted screening questionnaires. The better performing screening questionnaire with adequate sensitivity and specificity was adminitered to a nationally representative sample of survey subjects (n = 3364) to estimate the weighted prevalence of symptomatic KOA in Singapore.
Out of 146 subjects evaluated in the clinic, 45 had symptomatic KOA. A screening algorithm which consisted of three KOA symptoms or one symptom plus physician-diagnosed KOA produced high specificity (0.95, 95% confidence intervals [CI]: 0.88-0.98) but low sensivity (0.44, 95% CI: 0.30-0.60). Replacing the term 'KOA' with 'physician-diagnosed ageing-related knee problem' improved the sensivity (0.62, 95% CI: 0.47-0.76) without significantly compromising the specificity (0.87, 95% CI: 0.79-0.93). The prevalence of symptomatic KOA weighted to the Singapore population distribution were 4.7% and 11%, using the most conservative and more liberal algorithms, respectively. There was a sharp rise in prevalence after age of 40. The weighted prevalence of KOA was higher in women and among Indian and Malay than Chinese.
Our study adapted and validated questionnaires to the local context to screen for symptomatic KOA. We estimated the prevalence of symptomatic KOA in Singapore utilizing the better-performing algorithms.