Re: My Buddy just had knee replaced.
Absolutely, I've had my knee replaced, and my neck fused, and Wyoming is very ATV friendly. 1) Get an off road permit as they will check. 2) Stay on established roads, and tracks, no busting through the sage-not even for recovery. Antelope are pretty visible, and usually a cooperative one can be found without too much hiking. Not a bad drag weight wise, but the hair is different, slide it on a tarp or it will be bald on the down side within a 100 yards, the horns also pull off easy. A good walking stick is essential for him. Good kneepads as well.
Your buddies knee will feel much better in a year, I'm guessing he's been told that, I did this by myself last year so it's doable.
Tag is tougher, if you don't have preference points start by buying one now. Even 1 point can make a difference for a better unit these days. On sale until the end of September.
If he has doubts about what he'll be able to do in a year, and wants a first hand account I'll be glad to talk to him.