if you're truly concerned about your fellow man, or just don't want to be seen as a dickhead, i've found that waiting a bit and then asking "what hurts?" instead of an immediate "are you okay?" can yield some true information...I know when anyone's asked me "are you okay?," I immediately answer that I'm okay whether I'm okay or not.
but yeah if I don't know you and I think nobody's gonna track me down, I'm probably going to just say something about concrete don't owe you shit hellride etc