"The past few times have been painful in the knees, so I haven't pushed it,..."
Is the seat height correct? 10MM too low and my knees hurt! (I recently discovered after installing shorter cranks and forgetting to raise the seat) Check this link. I modify it a bit by just riding and getting some speed up. I then do the "heel thing" while pedaling forward.
http://bikenhike.com/page.cfm?pageid=23&FAQid=25
Also, ride every day, even if it's just around the block. It REALLY keeps you from "reverting" as much.