Assessing suspected viral arthritis
Arthritis due to a viral infection most commonly presents as a symmetrical polyarthritis, but the presentation can vary depending on the virus. Arthritis is rarely the only symptom of a viral infection and may not be the presenting symptom. Patients who have a viral infection typically also present with influenza-like symptoms, including myalgia, fever, headache and red eyes. Maculopapular rash is also common. Gastrointestinal symptoms (eg abdominal pain, diarrhoea) and lymphadenopathy are less common. In most cases of viral arthritis, symptoms peak at 1 to 2 weeks and are largely resolved by 6 weeks; however, occasionally, arthritis and myalgia persist for several months.
The main differential diagnosis of viral arthritis is early rheumatoid arthritis because this also presents as a symmetrical polyarthritis; however, in rheumatoid arthritis, symptoms are likely to be persisting without improvement, or worsening at 6 weeks. See Acute inflammatory polyarthritis in adults for an approach to the assessment of new-onset polyarthritis.
Monoarthritis is rarely due to a viral infection; promptly investigate a patient presenting with monoarthritis for other conditions, such as septic arthritis or gout, before considering a diagnosis of viral arthritis. See Acute inflammatory monoarthritis in adults for an approach to the assessment of new-onset monoarthritis.