Flexing the hip while also flexing the knee focuses most of the stretch on the knee joint. These first two videos demonstrate different ways to accomplish that. In the video below, notice how I am using my torso to generate the force needed to flex the knee. I then take up the slack created in the yoga strap with my arms. Also feel free to use your other leg to help generate flexion force as I demonstrate.
The next video demonstrates how to use the strap to improve knee flexion while keeping the hip extended. This is done in the prone position. This will focus more of the stretch on the quadriceps muscle. I recommend stretching in each of these positions for the best result.
Excellent knee function also requires full knee extension. The strap can help you achieve this as well. In the following video, I loop the strap over the knee to be stretched. I then place my other foot through a loop in each limb of the strap so that it does not touch the ground, but applies an extension force to the knee.
The use of a yoga strap for knee replacement rehabilitation is certainly not mandatory, but simply provides another option to assist you. Always remember to use ice after stretching, hold the stretches for as long as possible, and relax your mind and muscles as much as possible during the stretch.
Orthopedic Surgeon focused on the entire patient, not just a single joint.