| Good morning to you! Great that you want to jump back into a fitness routine, now that you have your doctor's permission.
I have not had knee replacement, and I am not a figure skater.
However, I do have a chronic knee condition for which I was given medical advice to avoid "pounding" & I am a hockey player, so I log miles of skating in any given week.
When I was first given a list of recommended activities, there were three categories:
avoid at all costs
could be ok, might not be, depends
no problem
Ice skating was in that middle category.
At the time, I found that the skating needed to play hockey was ok - if I wasn't pushing it too hard off the ice. If I tried to do any of the 'bad' activities (e.g., running, biking, downhill skiing, etc.), then I had problems even when I skated. Doing heavy powerskating work that required a lot of knee bend & attention to proper technique in my stride did cause pain, inflammation, etc. at a higher rate. I realize that when I was playing, I started to develop a stride with a bit less knee bend (and prob less power) to compensate for the injury.
Since that time, I have made major gains in the muscles surrounding the joint, gotten a fair bit lighter, & then gotten back to nearly the same weight (though with muscle instead of fat). I've also figured out what other 'triggers' make things worse for (e.g., diet, weather, etc.). I've made enough progress that I've been able to do things I never thought I'd be able to - like running a 5K for charity. Most important, I'm skating powerfully, pain-free.
My advice is that your biggest risk is not skating, but trying to do too much, too soon. I think ice skating can be a healthy component to a fitness routine. Take it easy the first times out & see how your body responds. I'd even suggest blading (in-line skating) first, as it is less stressful on the knees - but you already said you are in Denver, and I figure blading in Denver in January might be tough. Haha!
Good luck! Remember - you didn't put 40 lbs on in one week, so it won't come off in a week. But if you stay dedicated with your nutrition & activity, you WILL get back to a healthier place!  | 
