I need some expert advice on coding arthrocentesis and joint injection. A Medicare patient presents with an ear problem and knee pain. The physician addresses the ear problem then decides to drain fluid from the knee and inject it with Kenalog. My question is can he bill for the arthrocentesis and the injection? Both are coded as 20610. Do I use 2 units with a modifier? Do I bill them on separate lines with a modifier? Do I bill for the E/M with a 25 modifier, 20610 only once and the J code? Thanks for your responses.