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Updated: Jul 14, 2026
07:51
Synovial Fluid Analysis to Identify Osteoarthritis
Published on: October 20, 2022
Measurement of synovial fluid volume using urea
V B Kraus1, T V Stabler, S Y Kong
1Duke University Medical Center, Durham, NC 27710, USA. vbk@acpub.duke.edu
Osteoarthritis and Cartilage
|May 18, 2007
Summary
This study shows that urea concentration accurately determines synovial fluid (SF) joint volume in knees. This method is useful for quantifying joint fluid, correlating with knee pain in osteoarthritis patients.
Area of Science:
- Biochemistry
- Orthopedics
- Rheumatology
Background:
- Synovial fluid (SF) volume estimation is crucial for diagnosing and managing joint conditions.
- Accurate quantification of SF volume can be challenging, especially in effused joints.
Purpose of the Study:
- To evaluate the effectiveness of using urea concentrations to determine synovial fluid (SF) joint volume.
- To assess the utility of this method in both effused and non-effused knee joints.
Main Methods:
- Collected knee joint SF and serum from 159 osteoarthritis patients.
- Measured urea levels in SF and serum using an automated analyzer.
- Calculated SF joint volume using a formula based on urea concentrations and injected saline volume.
Main Results:
- Demonstrated an excellent correlation (r²=0.8588) between SF and serum urea levels.
- Found no correlation between urea levels/ratio and disease severity (KL grade) or inflammation (cell count).
- Observed a positive correlation between calculated SF volume and self-reported knee pain.
Conclusions:
- Urea concentration provides a reliable method for calculating intra-articular SF volume.
- This equilibrium between serum and SF urea is independent of disease status, inflammation, or age.
- The method's correlation with knee symptoms highlights its clinical utility for quantifying SF volume.
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