I am a 57 year old female. I play tennis about 3-4 times per week. Yesterday while playing, my knee felt tight or stiff. I usually just need to bend my knee quickly a few times and it will pop like cracking knuckles I guess. It did not work yesterday and just felt more stiff. As the day progressed it was stiff and now the next day it is very stiff when I try to bend it and is swollen. I cannot pinpoint the pain.... I push on spots and it does not hurt.... Maybe slightly on the outside of the knee. But just cannot bend it all the way..... So far I am only taking Advil and icing it....