Hi Terry,

I saw this YouTube video yesterday about a guy who has Lyme disease and had fluid on the knee as one of his major presenting symptoms I will post the link:
http://www.youtube.com/watch?v=tiZOF_jQe50&feature=user

Have you ever had a tick bite, which is the basis of Lyme Disease? There are lots of YouTube vids on Lyme.

Obviously there are probably many reasons for fluid on the knee but seeing that you have also been diagnosed with PN just thought I'd mention it!