Yes, if the back yard is common to multiple apartments (i.e., you don't have your own fenced-off area), then you can't put an antenna there. You have to stick to someplace other tenants can't go, like your patio, and I don't know how much room that'd give you (though even a small indoor antenna would perform better if there's less concrete & steel between it and the TV towers). But I'm confused. Are you saying your patio isn't contiguous with your apartment, so you'd have to run cable through a common hallway?
If that's the issue, you might consider something like
this. That would eliminate the cable. But you'd need electricity on your patio, a converter box, & a weatherproof housing for the converter box and sender unit. And this assumes your patio is on the "TV tower" side of your apartment building, otherwise there's not much point; even then it might be more trouble than it's worth.
This is the spot where I once again gripe about the lack of good indoor antennas on the market. Seems like someone could gang 4 or more UHF bow-ties into a largish, but reasonably flat, UHF antenna with a stand for indoor use. They could even include a loop sized for VHF-Hi; the combo might make an odd-looking piece of furniture but with a plastic housing to hide the "guts" I don't think it'd be particularly ugly; and it'd have at least some gain to help overcome common RF nightmares like this.