Abstract

Acute monoarthritis is one of the most common rheumatologic presentations. However, it is clinically difficult to distinguish between an inflamed joint due to crystal-induced arthritis and an inflamed joint due to septic arthritis. Arthrocentesis and synovial fluid analysis are used to differentiate between these 2 conditions. The presence of crystals and positive synovial fluid culture confirm the diagnosis of crystal-induced arthritis and septic arthritis, respectively. Although uncommon, these 2 arthritides can coexist, and presence of crystal does not exclude bacterial arthritis. We reported a case of 85-year-old woman whose synovial fluid contained crystals and was initially diagnosed with crystal-induced arthritis. However, her joint fluid culture subsequently grew Staphylococcus aureus, and she was treated with arthroscopic debridement and antibiotics.