Knee Effusions - Arthrocentesis Interpretation



Inflammatory arthritis:

 • Color: Yellow-> Green

 • Clarity: Opaque

 • Viscosity: Low

 • WBC/mm3: 2000->150,000

 • PMN's: > 50%

 • Mucin clot: Good to poor

 • Culture: Negative



Septic

 • Color: Yellow

 • Clarity: Opaque

 • Viscosity: Variable

 • WBC/mm3: 15,000> 200,000 

 • PMN's: ->75%

 • Mucin clot: poor

 • Culture: Mostly positive



Non-lnfiammatory:

 • Color: Yellow

 • Clarity: Transparent

 • Viscosity: High

 • WBC/mm3: 200> 2000

 • PMN's: < 25%

 • Mucin clot: Good

 • Culture: Negative



OTHERS:

 • Hemarthorosis- Large number of RBC's



Crystal analysis:

 • MSU: Gout

 • CPPD: Pseudogout



Additional DX:

 • Lyme: Serological testing

 • Gonococcal: Identify N gonorrhea via nucleic acid amplification of blood/synovial fluid

 • TB: Synovial membrane histo-anthology and culture

 • Fungal: Fungal stain and culture or synovial membrane histopathology



Dr. Ravi Singh @rav7ks



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