This is odd. I will explain as best as I can.
About a year ago, I experienced some sharp knee pain while running. It felt like my knee was about to just fall apart and my shin bone would just fall to the ground. I went to a doctor (expert, famous in GA) who said that it was IT Band syndrome. I did the stretching, it got better. No more pain. I would feel it slightly when doing stiff-leg deadlifts, but not to the extent that I felt it before.
Fast forward to more recently. I had been doing 5x5, and now doing Don Alessi's Meltdown Training. Deadlifting is a problem. I feel a sort of instability and weakness in my knee. It's not pain, just the feeling that something isn't right. On the last rep of the last set of Meltdown one time, when I locked out my left knee was literally shaking back and forth (forward/back to locked). Not good.
There is a click whenever I try to straighten my left leg. Also, it clicks when I stick my butt out and squat down a little, and then again when I stand up.
I had always thought it was a knee problem. Meniscus, ligament, something like that.
Then about a week ago, I was doing the weighted lunges as part of Meltdown. As I forward onto my left leg, lengthening the hamstring, I felt the same click except instead of in my knee, it was inside the meat of my thigh. It felt like there was a narrow segment of my hamstring that was clicking, and the whole thing clicked. Like a long tube of muscle, that clicked when I lengthed the hammy up to a certain point of the lunge. Very. Weird. Feeling.
So I guess it's not a knee problem?
Thread: Clicking Hamstring