I had a patellaectomy about three years ago and started developing similar symptoms: fever in the knee, red, swelling and quite a bit of drainage which was a clear to slightly yellow color.  Went to ER 1 day when the pain was unbearable and the ER had me sent immediately to my surgeon to have the staples removed.  He told me not to worry that it was only joint fluid leaking out of my leg.  My PCP, during a routing visit told me that indeed it was infected.  Started a regimen of antibiotics and 2 days later went to the ER again with excruciating pain and swelling that was double normal size.  Also had 2 large boils.  Spent 10 days in the hospital on drip and had the wound opened and cleaned by the gentleman that performed the patellectomy.  I would have chosen someone else but could not find anyone that would perform the second procedure when it was not their original work.

good luck