Need substitute for running.

[Miscthree]

Biopace will make a mad resurgence..just watch

 

[laxie16]

elliptical is great cardio while not straining the joints.

 

[MistaFreeze]

Jump rope!

 

[adlep]

Something that hasn't been suggested is rowing. Find a C2 concept rower and go for days. It'll work you hard and includes arms/back in addition to legs so it makes it a bit better overall workout tool.

For days?
If you are in shape, you can try to go for 30 min one day, but then you better take a break the next day, seriously...
My record was like 500 cal in 30 min and I almost passed out in the shower.

 

[waterduck]

I definitely recommend swimming. Have you ever thought about group fitness classes - boxing, martial arts? There is another sport that involves making everyday stuff into an obstacle course but not sure of what it is called.

 

[chr6]

i had the same problem, i changed to using an elliptical at the gym and i love it.