Repost: knee pain from walking?

I need help. I went walking around a lake today on a paved walking path. I was wearing shoes that are supposed to be good-Asics. The lake is about 6 miles around and I got 5 miles and couldn't finish. My knees were killing me. It was very painful and the pain seemed to be located on the sides of my knees. First it was the right knee, then the left. I didn't twist anything and I was only walking. Granted, that is much more exercise then I normally get.

I am wondering if biking would put less pressure on my knees and maybe I should do that instead.

Or will my knees just get used to walking as I continue to exercise?

Or do I need to put some gel soles in my shoes, etc

Please help. I'm posting this in more then one category so I can get more answers.