I have a noticeable limp the day after wearing heels & now my knee is sore to the touch & feels like there is cool water inside of my knee, what is it?

Possble fluid: You may have developed fluid on the knee from the shoes. Did you twist or turn your knee while wearing them. Try some anti-inflammatories and heat. If no resolution or your develop warmth in the area see your doctor, to see if it needs to be drained.

Injury: "fluid in the knee" is usually an effusion in response to some irritant. You may have arthritis or a meniscal tear. The heeled shoes may be putting a strain on your knee that flat shoes do not. If the pain persists, you may want to see an orthopedists for evaluation.