Question - knee injury (pop after kneeling)

by patricia schaller
(Boone NC)

I was bending down in a crouched position and when I stood my left knee popped very loud, there was a lot of pain and I could not stand on it for about 15 minutes. It did not swell. It started to feel somewhat better, but then I had to kneel on the floor and when I got up the same thing happened again. I have a little discomfort in the back of my knee a little to the left, but no big deal. I am afraid to crouch down or kneel for fear that I will get this terrible pain again and not be able to stand. I am wondering what I may have injured. Again, I have no swelling.