I am 27 years old and play tennis on a very regular basis. I have been feeling discomfort in my left knee area for the last 4 weeks. It doesn't really hurt when I walk or do any minor thing. But when I squat (or bend left leg and put my body weight on it) for more than 10-15 seconds and then stand up again, I feel pain close to the left knee. The pain goes away after I remain standing for a while. I am not really able to locate where exactly it hurts, but it's somewhere near the knee and the region slightly below.