http://probasketballtalk.nbcsports.com/2011/03/04/nate-robinson-out-4-6-weeks-with-knee-surgery/

Go ahead and ask if the Celtics knew about this before the trade if you want, it’s kind of moot. First, this seemed to come out of the blue. But really, Robinson was a throw in, Perkins was the goal and target. And they knew he was injured.