Regaining full terminal knee extension is paramount following any knee surgery. The ability to fully extend the knee equal to the other side is usually one of the most important early goals in knee rehab. While there are a ton of knee extension exercises you can do, the most important variable for regaining full terminal knee extension is the amount of volume and time spent working on knee extension. That is undeniably the most important concept to grasp. 3 sets of 1 min of stretches for a total of 3 minutes (out of 1440 minutes in a day aka 0.2% of the day) it just not enough end range stretching to regain full knee extension! Aim for a total of 10 minutes of knee extension exercises at first, then slowly keep adding time until you're spending at least 30 minutes a day working on terminal knee extension.