Im 33, and never had any problem with water on the knees. I went to the beach and got sunburnt aqnd all the sudden major pain. Anyone know what's this about?

The main cause of fluid on the knees is usually trauma. Did you bang your knee? Or over extend it? Or anything that may have strained it? If this is the case, give it some time, and put some ice on it, and an ace bandage and all should feel well once it has healed.

Another cause is osteoarthritis.


Either way. It is a good idea to see your doctor about it. :D