I haven't posted on here before but I have been an avid reader since I started C25K in March 2012. I graduated in May and have been running approx 3 times a week since then. But in the last couple of weeks my left knee has been twinging and I am wary about knees, I know how precious they are. What should I do, and why has it started to hurt? Do I stop running - becasue that would break my heart. I am totally addicted. I would really welcome any advice. Many thanks.