Suggest Treatment For Inflammation In The Knee

I'm am a runner who has had problems with inflammation in my knee in the past. The last time it flared up I went through therapy, NSAIDs, and insoles. None of it helped and I ended up having to stop running for about two years until it went away on it's own. I have ran a few marathons since I recovered, but now it's back. I don't want to wait another two years, I want to train and run. My question is, are Cortisone shots worth it? What kind of risk is there for weakening of the joint and tendon? If it's a real risk, I would probably wait it out again.

Thanks.