Why is knee extension important?
Proper knee function demands a strong quadriceps muscle which can support the body's weight when walking and running. This particular exercise is an open chain exercise - where the foot is free during the exercise, and should only be included once the patient is confident with closed chain exercises of the quads, such as mini-squats, where the foot remains in contact with the surface throughout the procedure.
Muscle inhibition may cause limitation of knee extension after injury or surgery due to "acute swelling, inflammation, pain, and joint laxity.....Preoperative full knee extension has been shown to be important in regaining postoperative knee extension and limiting arthrofibrosis...."