Non-Autoimmune Arthritis

Non-autoimmune arthritides—including osteoarthritis, gout, and septic arthritis—are common diagnoses in primary care settings. It is important to understand the prevalence of specific etiologies and to use the appropriate diagnostic modalities. A delay in diagnosis and treatment, particularly in septic arthritis, can have catastrophic results, including sepsis, bacteremia, joint destruction, or death.

The history and physical examination can help guide the use of laboratory and imaging studies. For example, the presence of focal bone pain or recent trauma requires radiography of the affected joint to rule out metabolic bone disease, tumor, or fracture. If there is a joint effusion in the absence of trauma or recent surgery, and signs of infection (e.g., fever, erythema, warmth) are present, subsequent arthrocentesis should be performed to look for inflammatory synovial fluid containing monosodium urate crystals. Noninflammatory synovial fluid might suggest osteoarthritis or internal derangement.

Pitfalls in the diagnosis and early treatment of non-autoimmune arthritis that must be avoided by the practicing physician include failure to perform arthrocentesis, administering antibiotics before aspirating the joint when septic arthritis is suspected (or failing to start antibiotics after aspiration), and starting treatment based solely on laboratory data, such as an elevated uric acid level.