Don't despair, Pat.
I'd been unable to ski without pain, effectively ending my skiing, since my first knee surgery in 1981 for torn medial meniscus, a leftover from my rugby days.
Four years ago this January I had a bilateral (both at once) TKR. Next month I'll begin my third year patrolling (skiing 3-4 x wk) at a small hill outside Detroit.
What you can/can't, should/shouldn't do with TKR depends on several things: your doctor, the type/brand device you receive and your fitness prior to the surgery.
Conventional wisdom for TKR patients is you can't do this or that and most doctors are very conservative. But my doctor, a true "sports medicine" specialist, said the only thing he wouldn't want me to do is run on hard surfaces. Post-op, I found that I actually could run -- something I'd been unable to do since that first surgery left me unable to fully extend on knee, which effectively made that leg a tad shorter than the other one. This eventually began to limit my ability to walk and was starting to give me back/hip problems on that side.
Through the 80s and 90s, while my son and daughter were still at home, I couldn't ski w/o pain, so I rarely did more than once or twice a winter. Unable to run, I'd turned to cycling to stay in shape, initially on a local trail on a mountain bike, then more avidly as a roadie since 2001, with total mileage some years between 4 and 5 thousand.
I'd know for many years I'd eventually need knee replacement but felt I couldn't jeopardize my job with a long rehab.
I was involuntarily retired in July 05, turned 60 that November and had the surgery the following January. My doctor is the orthopedic consultant for Detroit pro teams and insists on patients doing all they can pre-op to get legs in shape and has you out of bed, back on your feet the same day as surgery. The doc has a very rigorous rehab program, which I did 3 days a week with therapist, plus more at home, through April, when I was able to get back on my road bike.
He does the MIS (minimally invasive surgery) TKR. That's where the knee replacement and all the surgical equipment are designed for installation through a four-inch incision over the patella. This hastens re-hab significantly, compared to the old manner of TKR surgery, which a 12-14 inch incision through the quadricep.
Everyone's different, of course, and I've heard of TKR horror stories, including my much younger sister (her surgeon was the one I'd seen for years until finding the other guy 2-3 months before my surgery). I have brother-in-law a couple years older who flew back from Scottsdale for a double TKR from my surgeon 6 weeks after my TKRs.
In the mid-60s, he was one of our local ski bums, went to college summer school so he could spend winter semester in Colorado. So he was a big-time skier back in the day, but hadn't skiied for probably 10-12 years prior to his TKR, tho my sister (different one) still does. They've also got a place in Breck, but BIL won't ski because he doesn't want to risk anything, tho he's got a road bike and cycles regularly.
Last quick point, I'd ridden with a club several years and done some limited racing. Everyone who rides eventually has a fall and cycling shoes/pedals are clipped in (like ski bindings). So I asked my doc, what happens if I were to take a fall on my bike and not "clip out" in time, landing on my knee. So, he says, you land on your knee. It's not going to break.
I've also taken some falls skiing, since my on-hill SP training requires that I learn to ski all over again, unlearning my old knees and boots together style from the 60s and 70s.
Bottom line: TKR doesn't mean your skiing/riding days are done. Dunno about racing but that probably depends on how good a shape you're in prior to the surgery. If your surgeon says you can't ski after a TKR, find another surgeon. Mine is an ex-jock, looks 10 years younger than his actual age (late 30s) and understands that a lot of his patients don't want to get rid of an active lifestyle, just the pain.
When I called his office a year post-op to ask if the doc had any qualms about me skiing and joining the ski patrol, they said, "Nope. But be sure to send us a picture for our archives."
Good luck, Pat.