the thing with using a bike is that you have to work much harder to get your heart going, to mimic running you would need to work whole body like on a cross trainer or swimming hard, and you must do sprint work.
If you have a proper running track close by you could try their, depending on how bad your joints are because they are spongy.

remember when Hamed saisd he didn't do roadwork, spar for fitness. he may have been BS'ing but I found sparring harder than jogging.

Anyway-Deafman, I hope we've provided you with some ideas!