having gone through kneehab over 20 times (dislocations and 4 surgeries among both knees), and looking at possibly a TKR in a month, my recommendation is to get an xbox and halo, and take your frustrations out on aliens. once you can ride a recumbent exercise bike, pick one up from craigslist and keep playing halo until you can get out on the road again.

rehab sucks, but hopefully you don't have to get as good at it as i am.

oh, and if you DO take my advice, look me up on xbox live and we can while away the hours keeping the world safe.