red, swollen, knee cap

Hi,3 days ago my left knee cap became swollen, red, and sore to the touch. I can bend my leg at the knee just fine, but I cannot kneel down, as pressure makes the pain excruciating. Last night, I noticed that my right knee cap was redening and now it is in the same condition as the left. I am 26, and I have never had knee surgery. I hike everyday (about 3mi), twice a week I hike more about 5 or 6 miles.
I have not done anything different for the last 4 months, so why all of sudden the knee swelling and pain? Do my shoes have anything to do with the pain, they are about 5 months old? How can I make the swelling and pain go away? I am able to hike, but daily tasks are annoying due to my knee sensitivity. Thank You for Your Help,Jessica