Prevalence, risk factors, and impact of knee pain suggesting osteoarthritis in Spain

To estimate the point prevalence of knee pain suggesting osteoarthritis (OA) in the adult Spanish population. Secondary objectives were to examine the distribution of associated factors, as well as to assess the impact of knee pain on quality of life and function in the general population.

A population survey was conducted in year 2000 for which 2,192 subjects over 20 years of age were selected by stratified polystage cluster sampling from the censuses of 20 towns. Trained rheumatologists administered structured interviews that permitted them to rule out the presence of rheumatic symptoms, and which included validated instruments to measure function and quality of life. We used the definition of clinical symptomatic knee OA of the American College of Rheumatology.

The estimated prevalence of knee pain suggesting OA in the general adult population is 10.2% (95% confidence interval: 7.9-12.5). Elderly women with fewer studies and from the lower social class, as well as those subjects involved in physically demanding jobs are more frequently affected. Obesity is also an important determinant for knee pain suggesting OA. Knee pain is associated to a significant decrease in functional ability and quality of life, even after adjustment for age, sex, and comorbidity.

The prevalence of knee pain suggesting OA in the general Spanish population is higher than expected, mainly related to a high rate of knee pain in women over 55. The proportion of very old persons and of those obese are important factors to take into account when comparing the rate of knee OA between populations.