UMEM Educational Pearls

Title: Joint Fluid Analysis

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

Posted: 7/6/2008 by Michael Bond, MD (Updated: 11/22/2024)
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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.