Hey---I had both knees replaced on 11/08/07---and my left one now is just beginning to loosen up. I ride a bike, I lift weights, use rubber bands, and do balance work at the PT. Remember, you had major surgery and your muscles will be stiff for a while---maybe several months...but then they will get better.
I went back to teaching on 1/03/08. and throughout the day my knee would tighten and then loosen up---as in waves...but normally, by the end of the day, it was pretty tight. Remember, your knee didn't get this bad over night---and one point you need to consider (sorry for the pun!) is that you may have been slightly bow-legged---I was---and the leg is now straight---but the muscles have to adjust.
You have to be inths for the long haul. My MD andmy PT said it would be about a year before I forget that I don't have my real knees anymore. Did you get a chance to see what keeps megoing? It is my sons's commencement speech...
"If perhaps you get knocked down along the way, get back up! You must never accept failure! Never take the easy way out, and don't quit! If you have to, do it over and over again until you get it right. And when you get to that certain place where you are heading, BE COMMITTED. Be committed not only to your work or job, but to your family, your friends, and to yourself."
Things will get better! Slow down on your measurements---think of where you were last week or two weeks ago. I got frutrated too, but remember, you are recovering from major surgery.
Tim C.