Advice on good cardio for someone post knee surgery?

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I had my ACL replaced 2 years ago, and still have pain and stiffness on the right...and over-compensation on my left. Not back to running yet, as it leaves me in misery. Looking for a good cardio (other than swimming...that works GREAT, but I have no desire to put on a swimsuit and don't have access to a pool, anyway)...that would work for someone with a gimpy knee? I'm willing to do the work, but need to do it right! ;o)

(P.S. - friend me while you're at it! ;o) )