I negotiated the chairlift to the top of Snowmass without incident on a perfect blue-sky day in the Colorado Rockies. So far, so good. I took as deep a breath as a person can at 11,000 feet, pointed my skis downhill and made my first turn in the fluffy morning snow — on a brand-new titanium-and-plastic left knee.

A little wobbly. Was that me — after all, I hadn’t been on skis in a dozen years — or the knee? I stopped to regroup; the mountain was uncrowded, populated largely with adults. Happily, the young and the reckless were somewhere else.

I took another turn, this one on my right knee. That joint too had been retooled since I last skied. No problem! My trepidation ebbed as one confidence-building turn led to another, and I made my way down the gentle trail flanked with snow-sugared spruce.

I learned to ski in my 20s and had a good few decades loving everything about it: soft snow, crystalline air, heart-in-the-throat thrills, goofy camaraderie, all-encompassing physicality, the feels-so-good feeling at the end of the day and the jaw-dropping vistas you earn only by reaching the top of a mountain.

Then, playing touch football in the snow (ill-advised, I know, but so much fun), I snapped my right anterior cruciate ligament (A.C.L.), a sort of rubber-band-like stabilizer that runs through the knee joint, connecting the thigh bone to the shin bone.

Once the swelling subsided, the doctors said, I could live an active life without an A.C.L., including playing mild sports, bicycling and practicing yoga. I could, but gingerly. My knee wasn’t as dependable as I needed it to be. I went in for a new A.C.L. with a little meniscus trim thrown in on both knees. (Bear with me here. Medical play-by-play gets tedious fast, but this is what baby boomers talk about these days.)

After the requisite physical therapy, my doctor and I congratulated each other on the neat little scar and the procedure’s indisputable success. But, he warned, “You’ll be back. That left one is going to give you trouble. You’ve got a bone-on-bone situation brewing.”

Arthritis, in other words. The cartilage was shot. As predicted, running, yoga and even swimming soon became painful, and navigating subway stairs was a trial. Skiing? Not even on my radar.

The A.C.L. doc sent me to his colleague, the knee-replacement guy.

But wait: I wasn’t even 60. Wasn’t I too young for this?

“I tell my patients I’d have a knee replacement tomorrow if I was no longer able do any one of the things I am passionate about,” the dashing surgeon said. “In my case, that would be my work, bicycling or making love to my wife.”

Sold.

As it turns out, more and more people are getting new knees at earlier ages. (I will spare you the details of that operation; suffice it to say it involves a saw.) In 2010, there were nearly 700,000 knee replacements in adults over 45 in the United States, according to the National Center for Health Statistics. The operation has become streamlined: I spent one night in the hospital and went straight home; a visiting nurse checked on me a few times. Some replacements are now even outpatient procedures.

Two years later, everything seems possible again, with the exception of a couple of yoga poses. But skiing? I figured those days were over. I was newly remarried to a man who describes his one outing on skis as a daylong episode of the agony of defeat (Remember “Wide World of Sports”?)

And then a trip to Aspen presented itself. He had a speaking engagement (about obituaries, ominously enough), and egged me on to ski.

I checked in with my old friend the A.C.L. guy, who gave me a green light. “Do the groomers, blues and greens,” he advised. “Keep your ski fastenings on a looser setting, and stay out of the bumps.”

Day 1 for both knees was a triumph; no falling, no pain. Even the most onerous part of skiing — clomping around in the boots to get to lunch — had been pain-free.

I was hardly alone in the skiing-with-joint-replacement department. On one chairlift I chatted with a woman about 10 years my senior who had had both knees replaced and was back on skis the next season. “You’ll be fine,” she said. Later I rode up with a man about 10 years younger than I am, a local who’d already skied 20 days this season. He’d had a knee replacement three years earlier, at 47.

I did have one embarrassing moment on a chairlift when I looked down to discover I was wearing only one ski. I hadn’t even felt the other one come off. Blame it on those loose bindings. The threesome in the chair behind me held up my ski, grinning. Errant ski delivered at the top, I popped back into the bindings and resumed poking along on the blues.

On Day 2, with a steady, feather-light snow falling, I considered skiing Aspen Mountain, which I had done when I was younger (O.K., much younger), but it’s steep, with many narrow, harrowing black-diamond runs and a lot of the verboten bumps.

Snowmass, with 3,332 acres and 96 runs, is far bigger than Aspen and the other two mountains in the area, Buttermilk and Aspen Highlands, so I hopped the shuttle from the jolly Molly Gibson Lodge, our base on Main Street in Aspen, and returned. There were plenty of runs I hadn’t gotten to yet, including the enticingly named Naked Lady and Pure Bliss.

I also wanted to get back to Elk Camp, which borders a lynx preserve. No lynx spottings, but I skied for a while with a nature tour, with a girl with a stuffed possum on her hat.

I glided along on quiet trails, traversing a gorgeous little wooden bridge over a ravine, evergreens on either side, till the light turned flat and every muscle was gratifyingly tired.

My last chairlift of the trip took me over Makaha Park, where fearless youngsters twirled and flew over jumps and danced along skinny rails, landing — or falling — without a thought of bodily harm. It looked like so much fun. I have to admit, I envied their knees.