For arthritis or arthralgia there is no simple system for diagnostic analysis, but whether it is polyarthritis or monoarthritis, acute or chronic in onset, some general rules apply. Common causes include osteoarthritis (primary and secondary) and viral infection. Drugs should be considered, including those inducing gout. It is still imperative not to miss rheumatic fever, sepsis and tuberculosis in assessment. We may encounter more cases of Lyme disease presenting as arthritis.