I've never seen a crow here (Seattle) with a foot problem, but I wasn't aware of this problem until now. So, will keep my eyes open! I haven't seen aggression. Mostly, they are talking to each other, caw- cawing at each other. Or, seeming to care for each other.
About a week ago at my feeder, I did see a Junco that seemed to have an injured foot, or at least was limping. Haven't seen it since, however.