I found out about it right before surgery by watching a video put out by an orthopedic surgeon who stressed the importance of regaining extension and flexion during those crucial first 6 to 8 weeks after surgery and he showed the best exercises to do it. It scared me into being good about doing my PT and holding stretches for as long as I possibly could. I'm 6 months now and think I'm at 130ish but still working on it.