Arthrocentesis diagnostic chart
From WikiMSK
Arthrocentesis of synoval fluid
| Synovium | Normal | Noninflammatory | Inflammatory | Septic |
| Clarity | Transparent | Transparent | Cloudy | Cloudy |
| Color | Clear | Yellow | Yellow | Yellow |
| WBC | <200 | <200-2000 | 200-50,000 |
>1,100 (prosthetic joint) >25,000; LR=2.9 >50,000; LR=7.7 >100,000; LR=28 |
| PMN | <25% | <25% | >50% |
>64% (prosthetic joint) >90% |
| Culture | Neg | Neg | Neg | >50% positive |
| Lactate | <5.6 mmol/L | <5.6 mmol/L | <5.6 mmol/L | >5.6 mmol/L |
| LDH | <250 | <250 | <250 | >250 |
| Crystals | None | None | Multiple or none | None |
- Viscosity of synovial fluid may actually be decreased in inflammatory or infectious etiologies, as hyaluronic acid concentrations decrease
- The presence of crystals does not rule out septic arthritis; however, the diagnosis is highly unlikely with synovial WBC < 50,000[1]
- โ Shah K, Spear J, Nathanson LA, Mccauley J, Edlow JA. Does the presence of crystal arthritis rule out septic arthritis?. J Emerg Med. 2007;32(1):23-6.
