Why can you not jump after total knee replacement?
First of all, who told you that you can't?
Probably not a good idea to do that in early post-operative or rehabilitation period, but if the surgery goes well and there are no post-operative issues, there is no reason why you can't jump.
Of course prior to doing that you would have to build the strength back up in your quads and hamstrings.
TOTAL KNEE REPLACEMENT