Arthrocentesis Quick Look¶
Raeann Whitney
When in doubt, tap it!¶
-
Send synovial fluid for Gram stain/culture and cell count
-
Beware: Inflammatory / crystal arthropathies can have very high leukocyte counts!
- The presence of crystals does NOT exclude septic arthritis
-
A fever or concern for infection in a prosthetic joint is a surgical emergency; ortho will come in the middle of the night to tap a joint
-
Contraindications to tap: overlying cellulitis or psoriatic plaque
- Anticoagulation / DVT ppx is OK (no need to hold)
Arthritis Type | Appearance | Total WBC | PMNs |
---|---|---|---|
Non-inflammatory | Straw like / yellow | \<2000 | \<25% |
Inflammatory / Crystalopathies | Yellow / cloudy | >2000 (often 20-50K+) | >50% |
Septic | Purulent | >50,000 (often >100K) | >75% |
Crystals¶
-
Monosodium urate: needle-shaped, negatively birefringent
- Sensitivity is generally good (>90s%)
-
Calcium pyrophosphate dihydrate: rhomboid-shaped, positively birefringent (weakly)
- Weak birefringence significantly reduced sensitivity
Last update:
2022-06-27 03:29:20