Now that I'm in my 40's, I don't worry as much about things like perfect knees.
I think at some point, we need to just learn to get over ourselves and try to focus on the things that really MATTER. So your knees aren't pretty....do they work? Do they bend painlessly and carry you where you need to go? I used to hate my big legs and tall, strong body until the early morning that the drunk guy broke into my house and I had to fight him off, had to physically fight him to keep him from going down the hall to my son's bedroom. Believe me, when I was on the floor with my back against the sofa, kicking him away with my powerful legs, I was damn glad for the power and for my healthy knees. I think I might have even been grateful for my big feet for a few minutes.
Put things in perspective. Nobody's body is perfect, and anyway--why is it important that it should be? Why are we so focused on how we *look* as opposed to how healthy we are, and how productive we are in our society? Yes, I know women are judged on how we look. Know what I say? So what? We should be our best. Be healthy. Be strong. Be a contributing member of society. And either wear capri's or learn to appreciate your knees for the strong, healthy parts of your legs that they are.
For every girl that you are looking at with envy, there is most likely someone looking at you in the same way. It's hard to remember that sometimes, but it's true. We all have gifts and we all have flaws. It's just part of life.