knee problem with out pain!

Hi, I do alot of work on my knees. Over the weekend, just being at home relaxing I noticed that my left knee started getting real swollen, (below the patella area)there is no pain when I touch it, but it kept getting bigger. It looks red and it feels warm, but without pain. Is this something to worry about. When I touch it, it feels like a ballon filled with water underneath my skin. THe more I touched it, it just kept on getting bigger and bigger. Thanks for your response, i look forward to hear from you. Rosa