I found this after a search:

"Generally speaking, the length of your leg is governed by the medial and lateral collateral ligaments – the MCL and LCL. These are the large strap-like ligaments that run down the inside and outside of the knee. As a knee replacement doesn’t affect those ligaments, leg length remains unchanged."

Here is the link, with more information.
https://yorkshirekneeclinic.com/could-having-a-knee-replacement-alter-leg-length/
FWIW, I had both knees replaced this year and haven't noticed a leg-length disparity. I did wonder about it before surgery but never asked. I suggest you confirm with your surgeon.

All the best,

Joe