What are the two most common causes of chronic polyarthritis
a) OA: The prevalence of OA rises steeply with age. About 10% to 20% of people aged 40 years have evidence of OA, and 75% of women aged > 65 years have OA. This very high prevalence makes OA the single most likely diagnosis in older patients complaining of polyarticular pain who have noninflammatory signs and symptoms.
b) RA: The prevalence of RA among Caucasian populations in the United States is approximately 1%, making it the most common chronic inflammatory joint disease.