Cycling is the next best thing. You get outside, can do it on roads or trails, it's very aerobic and you can get in the zone, etc, but it really sucks in the winter time if you live anywhere cold. Actually, it's pretty much impossible in the winter if there's much snow. It also never brought the same sort of pleasure as running for me, but everyone is different.
Sorry to hear about your injuries. I would just try out different things. I've found it helps to do several different "sports" because then if one goes amok it's not as big of a deal, plus there're more opportunities to get out and have fun if you do a lot of different things. You could try cycling, swimming, weights, yogo, pilates, rock climbing, various classes, martial arts, etc.