Cycle. Don't run. Running is no good for your knee if it already has issues. Running is no good for your knee if it don't have issues. I went through this same deal for about 10 years and finally hade surgery. Orthoscopic and I was on a bike (instead of running) in 2 weeks. Best move I have ever made. Surgery is not for everyone but get a professionals opinion (or two). Stick with a professional that specializes in sports related injuries if possible.