Action
Perform arthrocentesis (Class I)
Decision
Succesful tap
Results consistent with septic arthritis?
Yes
- Provide antibiotics and admit
No
- Treat other diagnosis
Dry tap
Provide antibiotics and admit
Background
Arthrocentesis Interpretation
Attribute | Normal | Inflammatory | Septic |
Color | Clear/yellow | Yellow/white | Cloudy/opaque |
Viscosity | Thick, sticky | N/A | Thin, water-like |
sWBC | <25,000/mm3 | N/A | >1100/mm3 if prosthetic joint
>25,000/mm3, LR = 2.9
>50,000/mm3, LR = 7.7
>100,000/mm3, LR = 28 |
sPMN | <10% | <25% | >64% if prosthetic joint
>90% if native joint |
sLactate | <5.6 mmol/L | <5.6 mmol/L | >5.6 mmol/L, LR = 2.4 to infinity |
sLDH | <250 U/L | <250 U/L | >250 U/L |
Culture | Negative | Negative | Positive |
