My knee went whilst dancing last night. A real sudden sharp pain. It came and went within seconds and I carried on dancing.

However it then happened twice more during the night and by the end I could hardly bear weight on it.

It's kept me awake all night and 'pops' if I straighten it or bend it. I can only bend it to around a sitting position. Any further back than that (either by trying to move it or by moving it with my hands) results in sharp pain.

Any ideas?