My dad has a long history of gout. his foot and knee have been pussing. what could this be m what could cause it?

Not Gout: If it has pus draining...It isn't gout. It needs to be checked out right away. You need to make sure there isn't an infection.

Tophi: If the discharge is white and is not associated with pain or swelling, it is possible that your father has tophi lesions which are common for long-term gout patients. These are benign. But in any case i would have a doctor look at them to confirm.