http://www.youtube.com/watch?v=lptGKJLwW-8&feature=fvwrel Dr. Anthony describes runner's knee (patello-femoral syndrome) and shares how it is treated. Dr A mentioned in the video that a runner coming back from a long break, changing shoes/routines, and etc. suddenly can get this kind of inflammation. Makes me think that I should stick with my favorite shoes, rackets, and strings. And if I do make changes, I need to have a schedule to adapt to them. It also makes me realize why players don't change their equipment too much. They are optimized with what they have. Any change can require an adoption period or risk injuries.