Hi, since 2008 I have been an avid runner and soccer player. For example, in 2009 I ran the half marathon and played soccer all in the same day. In 2010 I ran the full marathon which was 42k and played soccer all in the same day. Generally on average I played soccer 3 times a week and before soccer on average I ran either 8k or 13k before soccer. I also injured both my knees twice playing soccer. I am ow trying to get back into running but after 45 minutes of running i have knee pain like a burning sensation and it is hard going down stairs. I am won=dering if perhaps it is wear and tear from just overuse of running over the years