Hi, guys! I have been playing every day for ~4 hours a day and recently started getting problems in my left knee, where I feel a "crunch" whenever I straighten my leg from a bent position -and vice versa. I have a 2-handed backhand, which requires me to bend my left knee quite a bit and push off in order to hit a lot of balls. If I ignore my knee crunch (ive had it for the past week now) and play regularly, eventually I start getting a dull pain inside the knee. This forces me to stop doing 2 handers, and hit one handed backhands without bending my left knee (which I don't like!) I am fairly sure that this is not a problem with mechanics. Any one else had this before? Based on this information, would you say some leg strengthening exercises are in order? Thanks so much!