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Nongonococcal Infectious Arthritis Workup

  • Author: Edward Dwyer, MD; Chief Editor: Herbert S Diamond, MD  more...
Updated: Mar 15, 2016

Approach Considerations

Leukocytosis is common in patients with acute bacterial arthritis. Approximately 50% of persons with acute disease exhibit white blood cell (WBC) counts higher than 10,000/µL. Blood culture results are positive in approximately 33%-50% of patients with nongonococcal bacterial arthritis.[8]

If indicated, arthrocentesis for synovial fluid analysis is the single most important diagnostic procedure for evaluating infectious arthritis. It allows culture and appropriate microscopic examination of the synovial fluid and tissue.

Diagnostic imaging modalities may be helpful but are often nonspecific.


Arthrocentesis and Synovial Fluid Analysis

The synovial fluid cell count is generally higher than 50,000/µL, with neutrophils predominating (>90%) in persons with acute bacterial arthritis.

Results of a Gram stain of synovial fluid are positive in approximately 75% of patients with staphylococcal infections but in only 50% of patients with gram-negative infections.

A microscopic examination of synovial fluid for monosodium urate crystals and calcium pyrophosphate crystals is performed to exclude crystal-induced arthritis (eg, gout or pseudogout). It is important, however, to be mindful of the possibility that infectious arthritis and crystal-induced arthritis may be coexisting in a single joint, though such coexistence is reportedly very uncommon.

Culture of synovial fluid should be performed for aerobic and anaerobic organisms. Inoculation of blood culture bottles is more sensitive than culture on solid media, especially in patients pretreated with antibiotics.[9]

Biopsy of synovial tissue for culture and histologic examination is important if mycobacterial or fungal infections are suggested. Culture of synovial fluid is an insensitive diagnostic test in this setting.


Radiography, CT, MRI, and Radionuclide Imaging

Plain radiography is generally nonspecific and may reveal only a joint effusion in the early stages of infection. Cartilage destruction and joint space narrowing are late findings and may be difficult to interpret if there is a preexisting joint disease.

Computed tomography (CT) may help diagnose sternoclavicular or sacroiliac joint infections. Magnetic resonance imaging (MRI) is most useful in assessing the presence of periarticular osteomyelitis as a causative mechanism.

Radionuclide studies (eg, bone scans) yield positive results for any inflammatory arthritis and thus have poor specificity. They may be useful for diagnosing sternoclavicular or sacroiliac joint infection.

Contributor Information and Disclosures

Edward Dwyer, MD Associate Professor of Medicine, Columbia University Medical Center

Edward Dwyer, MD is a member of the following medical societies: Alpha Omega Alpha, American College of Rheumatology

Disclosure: Nothing to disclose.

Chief Editor

Herbert S Diamond, MD Visiting Professor of Medicine, Division of Rheumatology, State University of New York Downstate Medical Center; Chairman Emeritus, Department of Internal Medicine, Western Pennsylvania Hospital

Herbert S Diamond, MD is a member of the following medical societies: Alpha Omega Alpha, American College of Physicians, American College of Rheumatology, American Medical Association, Phi Beta Kappa

Disclosure: Nothing to disclose.


Elliot Goldberg, MD Dean of the Western Pennsylvania Clinical Campus, Professor, Department of Medicine, Temple University School of Medicine

Elliot Goldberg, MD is a member of the following medical societies: Alpha Omega Alpha, American College of Physicians, and American College of Rheumatology

Disclosure: Nothing to disclose.

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Medscape Salary Employment

Robert E Wolf, MD, PhD Professor Emeritus, Department of Medicine, Louisiana State University School of Medicine in Shreveport; Chief, Rheumatology Section, Medical Service, Overton Brooks Veterans Affairs Medical Center

Robert E Wolf, MD, PhD is a member of the following medical societies: American College of Rheumatology, Arthritis Foundation, and Society for Leukocyte Biology

Disclosure: Nothing to disclose.

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