My wife recently had knee surgery to remove a metal rod in her lower leg following a serious break a few years ago. The surgery (3 operations in all) has really wrecked her knee (note to self - get private health cover

)
Her advice:
* Go to a sports physiotherapist. The advice and treatment from them has been invaluable to her as she slowly returns to training. She estimates its taken months off the rehabilitation.
* Train lightly - any decent instructor will allow you to train at your own pace for as long as required (hey - we're happy you turned up!!!

)
* Beware of swelling and listen to your knee. It will tell you when to pack it in - dont ignore that!
* Heat treatment
* Strengthening exercises as advised by physio
Good luck mate - hope it all mends quickly for you!