In addition to the usual rehab work, very early after surgery I used the bike on a trainer to help with increasing range of motion. I raised my saddle and just rocked back and forth until i could make a full revolution then once or so a day I spent time just pedaling under no to light load. It helped significantly to return range of motion and reassure me that I could cycle again. Eight weeks was about the earliest I felt comfortable in going out on the roads again and even then I was cautious, but it worked out. The main point is not to push too much too soon and delay recovery with a series of set backs, something that seems to be very usual for those of us with knee replacements. Good luck and keep riding....