In this video, Alex is demonstrating how to perform a Heel Slide.
If you are unable to perform this exercise, see Heel Slide Using a Leg Strap.
If one of your precautions is "No bending greater than 90 degrees at the hips", use caution not to break this by leaning too far forward in placing the strap around your foot. Additionally, keep your heel on the surface that you are lying on as your perform the heel slide in order to prevent breaking the above precaution as well. Check with your surgeon and/or physical therapist on the appropriateness of this exercise after surgery. Depending on your surgery, some surgeons may initially hold this exercise after surgery.