Osteoarthritis (OA) is an important cause of longterm health problems and the most frequently reported reason for longterm disability in the population. The overall prevalence of reported arthritis (mainly OA) was 18% of the Ontario household population (age > or = 16 years), with 2.5% of the population reporting longterm disability. An appreciable proportion used health care resources and continued to do so over the long duration of the condition. Longterm disability was accompanied by a substantial effect on daily life, including troubles with mobility, dependence, and difficulty with everyday living activities, social isolation, curtailment of leisure and employment activities, and low income.