I have a bad knee, the doctor basically said the bones in my knee is scraping against the cartilage, and the best thing to do is strengthen the muscles around it.

I'm looking into getting a bike to start straightening my legs to hopefully help my knee.

I want to get a fix gear but I know nothing about them or what I should get.

Can someone give me some pointers..

I read this replying to someone with a bad knee?

In order of importance:
Make sure your bike fits you.
Choose an appropriate gear
Use a brake.

Since I have a knee problem already should I stay away from getting a fix gear?

What size bike would fit me?? I'm 5'8 - 140 pounds - 23 years old.

What an appropriate gear for me? (a newbie thats never ridden with a bad knee)

Any help would be awesome!!

thanks