I'm so excited for you, your new knee looks great! I was also knock-kneed, not as severely as your before picture, but yes, the hamstrings and calves took a while to stretch after my surgery. I did have a prescription for muscle relaxers and those really helped in the first couple of weeks when I had spasms and cramping in my hamstrings, calves, and quads. (Edited to add - stay hydrated! I could tell when I wasn't drinking enough water because the cramping and spasms were definitely worse! Also getting up because I had to pee all of the time seemed to help make sure I didn't stiffen up too much)
Yay for new straight knees!