A few gyms have handcycles (upper body ergometers) which are basically exercise bikes, except that they're configured so that you pedal with your arms instead of your legs. Of course one's arm muscles aren't as strong as leg muscles, so it's not as efficient a workout. However, it is aerobic. Try it out if you have access to one.
Another option, if you're well coordinated, is to pedal a standard exercise bike with just one leg. It can be done if you are able to fold or prop the injured leg out of the way, and are careful with your technique.
If all else fails, you can still do upper body weight work, along with core strengthening.
"...I've learned that you shouldn't compare yourself to the best others can do, but to the best you can do....I've learned that you can keep going long after you think you can't..." --- author unknown
2013 highlights...
@ 5K:
Ontario Mills 5K, Ontario, CA, 24:42
Heart of the City Run, Los Angeles, CA, 24:13
Downtown Anaheim 5K, Anaheim, CA, 24:32
@ 10K:
LA Chinatown Firecracker 10K, Los Angeles, CA, 51:42
The Great Race - Old Agoura 10K, Agoura Hills, CA, 51:12
Fiesta Days Run, La Canada, CA, 49:31
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