This is only afffecting my left leg. During exercise 17, hamstring lunge and variations, I am experienced knee pain. As I push my body away from my left foot and straighten my leg, in order to intensify the stretch in my hamstring, I begin to feel a growing pain on the lateral and medial aspect of my knee. I don't feel a stretch in my hamstring at all prior to feeling the pain or during it. I'm guessing this could be due to calf tightness or just by me over doing the stretch and not taking enough rest? I also feel this sensation when I, from a standing position, flex at the waist and place my palms on the floor. When I begin to extend my knees I feel the same sensation. With no sensation in my gluteus or hamstrings.