Any doctors or sports medicine people in the house?

[tiger88 934]

All of the sudden I have a strange and very painful knee ailment. I never felt the injury happen. Here is what it is. I can felx my right leg fine, there is no pain at all. I just can't flex it and put pressure on it at the same time. When I do I get a massive shooting pain on the back of the right side of my knee. When I walk stiff legged there is no pain at all. Only when bending and putting pressure on it and it hurts so bad I can't take a step like that?

I have a feeling it's ligament related but that's a guess.