Sore knees, asthma help!

My knees have always bothered me even when I was a kid. I've also had breathing problems/asthma since I was a kid as well. When I'm laying in bed for the night my knees ache, mainly my right one, especially if I've done a workout or walked a lot that day. My grandmother had breathing problems and bad knees as well so I'm just wondering how to prevent my sore knees and keep them from becoming damaged so soon, I'm only 25 and want to be sure I'll be able to walk and run freely for a long time.

Also, I have an inhaler I take before I exercise but it doesn't really help and my asthma holds me back from giving it all I've got, it's really frustrating. Anybody have any tips on managing asthma? I've heard stories of people overcoming their asthma the more fit they become. I don't know if that's possible but I would be so ecstatic!