Monoarthritis: inflammation of a joint (arthritis) that occurs in one joint at a time. Infection, trauma, and crystal-induced arthritis (for example, gout, pseudogout) are the most common causes of monoarthritis. SLIDESHOW What Is Rheumatoid Arthritis (RA)? Symptoms, Treatment, Diagnosis See Slideshow From Arthritis Resources Inside the Visit With a RheumatologistTreating Psoriatic Disease With BiologicsRA and Your Joints Featured Centers What Are the Best PsA Treatments for You?Understanding Biologics 10 Things People With Depression Wish You Knew Health Solutions From Our Sponsors Shot-Free MS Treatment Your Child and COVID-19 References Longo, D.L., et al. Harrison's Principles of Internal Medicine, 18th ed. United States: McGraw-Hill Professional, 2012.