UMEM Educational Pearls

Category: Orthopedics

Title: Joint Fluid Analysis

Keywords: Arthrocentesis, Joint, Fluid, Septic (PubMed Search)

Posted: 7/6/2008 by Michael Bond, MD (Updated: 6/13/2024)
Click here to contact Michael Bond, MD

Joint Fluid Analysis:

This is hte session in Baltimore for crab eating and beer drinking so we begin to see an increase in Gout pain.  For those that are presenting with their first episode and you are concerned that they might have a septic joint, I am including this pearl to help analysis the fluid you will obtain from arthrocentesis.

 

Synovial Fluid Interpretation
Diagnosis Appearance WBC PMNs Glucose % of
Blood Level
Crystals
 Normal  Clear  <200  <25  95 - 100  None
 Degenerative
Joint Disease
 Clear  <4000  <25  95 - 100  None
 Traumatic
Arthritis
 Straw colored  <4000  <25  95 - 100  None
 Acute Gout  Turbid  2000 - 50,000  >75  80 - 100  Negative birefringence
 PseudoGout  Turbid 2000 - 50,000  >75  80 - 100  Positive birefringence  
 Septic Arthritis  Purulent / turbid  5000 - > 50,000  >75  < 50  None
 Rheumatoid
Arthritis
 Turbid  2000 - 50,000  50-75  ~75  None

 To view a gout crystal click this link.

To view a pseudogout crystal. Click this link

Pearls: 

  • A WBC Count >50,000 is septic arthritis until cultures are negative. 
  • Due to the wide range of WBC for septic arthritis have a high index of suspicion and do not discount the diagnosis because the WBC count is only 10,000.

References

Benjamin GC. Arthrocentesis. In: Roberts JR, Hedges JR, eds. Clinical procedures in emergency medicine. 3rd ed. Philadelphia: Saunders; 1998:919-932.