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Synovial Fluid Analysis of Knee Joint

Last updated Oct. 12, 2015

Pain originating in the knee area just above the knee.


What are the other Names for this Test? (Equivalent Terms)

  • Knee Joint Fluid Analysis Test

What is Synovial Fluid Analysis of Knee Joint? (Background Information)

  • Synovial fluid is a thick substance found in the major joints of the body (such as the shoulder, hip, elbow, wrist, knee, and ankle), most notably in the knee. It acts as a lubricant, shock absorber, and nutrient medium
  • A joint links the ends of bones together and enables them to articulate or move against one another. However, the bones do not physically touch each other, as this would cause bone degradation and pain. Instead, the articular surfaces of bones are covered by articular cartilage. This is a smooth form of cartilage that is less dense and thus slicker than other cartilages
  • The synovial fluid fills the spaces between articular surfaces within the joints. Articular cartilage is also permeable to synovial fluid. This enables the two to work together to provide further joint protection
  • When articular cartilage is compressed, it pushes synovial fluid out and into the joint, where the fluid can lubricate the opposing surfaces. When compression is relieved, the fluid re-enters the articular cartilage. Similarly, synovial fluid acts as a shock absorber. Forces felt by the joints are spread across the synovial fluid, lessening stress on the articular surfaces
  • Another important function of synovial fluid is to exchange wastes and nutrients with the surrounding capillaries. This allows for proper maintenance of the joint tissue
  • The joint disorders are categorized into 5 groups:
    • Non-inflammatory
    • Inflammatory
    • Crystal-induced
    • Septic
    • Hemorrhagic            
  • The Synovial Fluid Analysis of Knee Joint evaluates several aspects of the synovial fluid to assess joint health and differentiate between different types of joint disorders. The aspects evaluated include:
  • Appearance: Color, turbidity, and other visual properties
  • Chemistry: Glucose, pH, proteins, lactic acid, and uric acid
  • Microscopic examination: White blood cells, red blood cells, and polarized light analysis to detect crystals
  • Infectious disease analysis: Gram stain, culture, and smear to detect pathogens 

What are the Clinical Indications for performing the Synovial Fluid Analysis of Knee Joint?

Following are the clinical indications for performing a Synovial Fluid Analysis of Knee Joint:

  • Following-up to a physical examination
  • Monitoring a joint disorder
  • Recent injury
  • Swelling
  • Redness
  • Pain

How is the Specimen Collected for Synovial Fluid Analysis of Knee Joint?

Following is the specimen collection process for Synovial Fluid Analysis of the Knee Joint:

Sample required: Synovial fluid of the knee joint

Process: Insertion of a needle into the knee joint (arthrocentesis of knee joint).

Preparation required: No special preparation is needed prior to the test. 

What is the Significance of the Synovial Fluid Analysis of Knee Joint Result?

The significance of Synovial Fluid Analysis of Knee Joint is explained:

  • Increased white blood cells, microorganisms, lactic acid, uric acid, and/or crystals in the synovial fluid may indicate:
    • Gout
    • Pseudogout
    • Osteoarthritis
    • Acute bacterial arthritis
    • Rheumatoid arthritis  
    •  Hemophilic arthritis  
    • Tuberculous arthritis   
    • Systemic lupus erythematosus
    • A significant trauma      

The laboratory test results are NOT to be interpreted as results of a "stand-alone" test. The test results have to be interpreted after correlating with suitable clinical findings and additional supplemental tests/information. Your healthcare providers will explain the meaning of your tests results based on the overall clinical scenario. 

Additional and Relevant Useful Information:

  • The synovial fluid analysis of a joint involves the testing for uric acid and glucose levels. In order to assess the overall levels of uric acid and glucose in the body, additional blood and urine tests for these chemicals may be performed
  • Your healthcare provider will combine the findings of the blood test, urine test, synovial fluid analysis, and the overall clinical signs and symptoms to arrive at a diagnosis 

Certain medications that you may be currently taking may influence the outcome of the test. Hence, it is important to inform your healthcare provider of the complete list of medications (including any herbal supplements) you are currently taking. This will help the healthcare provider interpret your test results more accurately and avoid unnecessary chances of a misdiagnosis. 

What are some Useful Resources for Additional Information?

DoveMed is currently working to bring you additional resources.

Please sign up by creating a DoveMed account to receive periodic notification on information updates. 

References and Information Sources used for the Article:

Lab Tests Online (2014, July 21). Retrieved November 29, 2014 from http://labtestsonline.org/understanding/analytes/synovial/

Martini, F., Nath, J. L., & Bartholomew, E. F. (2012). Fundamentals of anatomy & physiology (9th ed.). San Francisco: Benjamin Cummings.

Schnell, Z. B., Van, L. A., & Kranpitz, T. R. (2003). Davis's Comprehensive handbook of laboratory and diagnostic tests: With nursing implications. Philadelphia: F.A. Davis.

Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: Nov. 29, 2014
Last updated: Oct. 12, 2015