It looks like you're shortening up your extension at the top. Keep pushing through the ground as long as you can. Something Greg told me that has always helped me finish my pull is to think about finishing with my shoulders behind my hips. I suggest doing some snatch/clean pulls and really focus on finishing that pull.
You're also diving through in the bottom position. It looks like it make be an ankle mobility issue or a lost range of motion in the knees from surgery. Do some ankle stretches before your lift and I would also suggest doing some Zots presses before you snatch and really focus on keeping your torso as upright as possible.
But all around it looks like you move pretty well after having knee surgery.