Hey Brandi - sorry about your hubby's knee! Hope the surgery goes well. I only use a Cyclops fluid trainer for road bikes. But as far as I know, you can switch out your bikes, just need to adjust for the size of the rear hub. Maybe you should post this question on the Mt bike section to see what the girls seriously into dirt recommend! It is fun to ride trainers together, but kind of expensive. Another option if you ride a road bike is to use rollers. If you don't know if you would like rollers, try to find a friend who will let you (teach you) how to use them. they are FUN! There might be a bike store that might have some rollers or know someone with rollers who could help you. Good luck! tokie