Welcome to HCM
We understand your concerns
I conclude that you are healthy individual with just the mentioned symptoms present.Flu
and hot flashes around knee and ankle might not be connected. But it is also possible in the case when you are overly tired due to flu and had some impact on these areas. Check yourself up for arthritis
if there is also burning sensation, swelling, grinding pain, hue color change etc. If flu is continuing even after antibiotics, you must visit your GP. You need follow up treatment.
Get well soon.