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Acute Monoarthritis: Diagnosis in Adults

This is a corrected version of the article that appeared in print.

Jeremy Swisher, MD
Zachary Sitton, MD
Kimberly Burbank, MD
Chris Nelson, MD

American Family Physician. 2025;111(6):497-506.

Author disclosure: No relevant financial relationships.

This clinical content conforms to AAFP criteria for CME.

Acute monoarthritis, characterized by pain or swelling in a single joint, is a diagnostic challenge in the primary care setting. Intra-articular conditions typically manifest with reduced active and passive range of motion, whereas patients with periarticular conditions such as tendinitis or bursitis often maintain passive range of motion. When evaluating a patient with acute monoarthritis, it is essential to remember that many polyarthritic processes can initially present in a single joint. A broad differential diagnosis for monoarthritis should include septic arthritis, osteoarthritis, gout, trauma, and Lyme arthritis. Of these, septic arthritis is the most urgent and requires prompt intervention. Bacterial culture of the synovial fluid is the most accurate diagnostic test for a septic joint. However, diagnostic accuracy can be increased in the short term by evaluating additional markers such as synovial white blood cell count, synovial lactate, and serum biomarkers. These supplementary tests aid in early decision-making while awaiting bacterial culture results. Osteoarthritis is often clinically diagnosed and may be confirmed with radiography. Gout, the most prevalent crystalline arthropathy, can be diagnosed using specialized calculators, ultrasonography, and dual energy computed tomography. Gout is typically most painful at night or in the early morning. Ultrasonography is useful for identifying effusions in less-visible joints and facilitating precise joint aspiration.

JEREMY SWISHER, MD, is a sports medicine physician in the Division of Sports Medicine at the University of California, Los Angeles.

ZACHARY SITTON, MD, is a sports medicine fellow in the Department of Orthopaedic Surgery at Duke University, Durham, North Carolina.

KIMBERLY BURBANK, MD, is a family medicine resident in the Department of Family Medicine at Atrium Health Wake Forest Baptist, Winston-Salem, North Carolina.

CHRIS NELSON, MD, is an assistant professor in the Department of Family Medicine at Wake Forest University School of Medicine.

Address correspondence to Jeremy Swisher, MD, at jeremyswisher.medicine@gmail.com.

Author disclosure: No relevant financial relationships.

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