Does anyone else have an ab circle pro?

tjs22

I was wondering what you thought of it. I got mine two years ago and recently pulled it out, dusted it off and used it once and then it came back to me.. I quit using it in the first place because it KILLS my knees. I used it yesterday for 3 mins and today they feel bruised. Im only 20 lbs overwieght. I love the work out just not the pain. I've been trying to think of a way to pad mt knees any ideas? It cost $200 and I would like to get some use out of it!