RESUMO
Abstract Arthritis in childhood is common. The pattern, presentation and duration of arthritis help differentiate between the various possible diagnoses. When only one joint is involved, i.e., monoarthritis, it may be difficult to make a diagnosis as there are many possibilities both acute and chronic in nature. A detailed history and clinical examination is important to reach a correct diagnosis and the single most important investigation when a child presents acutely is a joint aspiration to rule out septic arthritis that may destroy the joint in hours. Inflammatory markers, antinuclear antibody testing, test for tuberculosis and imaging (in specific cases) play an important role in the diagnosis of a child that presents with a chronic monoarthritis. In this article we provide a clinical approach to the diagnosis of monoarthritis in a child.