One swollen ankle with no cause

[Lushmetender]

I've been running but I have one swollen ankle but no obvious reason for it. Any ideas? Been running since Feb but only 30 minutes twice a week. I'm 46 and training for a triathlon but had no injuries- any ideas?

is it painful?
any redness?
does it feel warmer than the other ankle?

Are you ok today op? I’d get to a dr if I were you if you’ve not already been

Hi it's not painful and even jogged on it. Just concerning it appears to be swelling for no reason. No redness. The tendon further up my leg was tender but that has gone. My mum has rheumatoid arthritis which started around this age so a bit concerned ( I have ulcerative colitis which is genetically connected to RA). So mybieest worry