Joint Swelling and Fever

Yesterday morning, I was hit by a baseball on the inside of my knee causing a great amount of pain. Later in the day, the knee swelled up and I iced it. I also started running a low fever (100.5 F) that was reduced by taking Advil. Now, more than 24 hours later, the swelling has not gone down. I can?t put much weight on the leg. If I stop taking Advil, the fever returns. Are my symptoms related to each other or is it just a coincidence that I became feverish at the same time I got hit?