Anterior and Posterior Capsule Stretches, Dr. David Privitera

Knee Terminal Extension Stretch

Lay on a firm couch or table with padding, stomach down with your knee caps just beyond the edge
While wearing shoes to allow for a more comfortable and effective technique, take your nonsurgical foot and push the surgical leg's heel down toward the ground, effectively straightening the knee with the controlled strength of your other leg. Since your kneecap is beyond the edge of the table, it will slowly force your knee into extension. Your surgical leg should be completely relaxed throughout the stretch.
Hold stretch for 20-30 seconds and then relax your surgical knee, by lifting up the surgical foot by hooking your nonsurgical foot underneath it, lifting, allowing the knee to passively bend
Repeat stretch 5-10 times, 2-3 times a day