My knees and my ankles hurt? =S?

it started this week, and it's really annoying. When i go down stairs my ankles will have pain in them and my kneez ( for kneez a bit) Like i use to be able to run perfectly but all of sudden i realized that my kneez and ankles hurt when i ran ?? im 16 years old, 5ft 8". I weight about 180 pounds, but this is normal i could run just fine with the same weight. Like when i ran i felt the pain a little but it's when i try to stop when it hurts. Just today i was running and after that there was alot of pain in my kneez and ankles. i just wanna know if this is something serious, like the pain is bearable, it doesn't hurt like mad or anything. It's just annoying. O and when i roller blade like even when i roller blade really fast, i dont feel that pain as often. It's only when pressure is put on it that it hurts. Going down stairs ect. pls hellppp!!! i dont wanna give up soccer, baseball, track, and ice hockey =(