Had arthroscopic ankle surgery a month ago. this foot looks darker than the other one. causes? is this normal? for how long will this last? thank you

Other symptoms?: You didn't mention whether there are symptoms of numbness, tingling, unusual pain (other than normal postoperative things since you're still relatively close to surgery), or difficulties with controlling movements...though at 1 month post surgery, perhaps you're not weight bearing but if all of that is normal then, what you see may not be that alarming. Still seeing the surgeon can't hurt, right?

Could be: There can be a variable degree of swelling, inflammation, and even bleeding that can follow a ankle arthroscopy, in part related to the nature of what was done. I would certainly let your surgeon know, particularly if it is getting worse; which can also be a sign of infection or even a blood clot.

Yes: Darkness is probably due to swelling after the surgery, which is normal. It should go away over the next few weeks.