I am an Emergency Physician. I have a 36 year old patient with rapidly progressive glomerulonephritis who has been on Rituxamab. He developed acute, immediate pain in his right knee earlier today. His labs and xray do not indicate septic joint. There is nothing else locally (no trauma, no cellulitis, etc), and he has nothing else constitutionally. We are going to tap the joint to ensure no septic joint. Our strongest consideration is acute crystalline arthritis (ie, gout); should we be considering other entities? We have withheld antibiotics, but have given him decadron, fluids, and he has required dilaudid for pain control. Dr. Paul Blackburn, Emergency Department, Maricopa Medical Center, Phoenix YYYY@YYYY