Mine was 5 years ago at Alta.
I was heading out to Snowbird for a final fling before my daughter was born - four days of skiing my favorite mountain before scaling things back for the rest of the season. My 7.5 months pregnant wife told me to go and have some fun for a few days and she'd take care of our 2 year old son while I was away. Looking back at it, I feel like a bit of an ass for even going at that time. Maybe the injury was karma.
I was meeting two friends in SLC. Independently, they both wound up having to delay their flights for a day because of work. I didn't want to change my flight, and don't mind skiing by myself, so I went as scheduled, I figured I'd take the opportunity to ski Alta seeing I wouldn't get to ski it while I was with my friends (they're snowboarders).
The day started ominously. I was staying at a hotel in Sandy, and while walking to my car, slipped on some black ice and hit the ground pretty hard. No real injuries, just a bit sore. I got myself and my gear back together, loaded up and headed to the mountain, getting there around 8.30am. I booted up and went skiing. The snow was fine, but nothing special. It hadn't snowed in a few days, but everything was still pretty soft. The light conditions weren't great though. Super flat light, and difficult to see nuances in the terrain.
I skied for a couple of hours, taking it pretty easy, and was planning to make one last run before taking a break to get something to eat. I wasn't skiing fast (maybe 20mph) on fairly mellow terrain about halfway down the mountain, when I hit a snow covered ditch a couple of feet deep running across my line. I had no idea it was there until I hit it, and I got absolutely launched by it. I went straight over the handle bars, through the air, and tomahawked a couple of times. I'm not sure if it was after the initial impact or after one of the tomahawks when I heard a loud pop as I was in the air. It turned out the pop was from my right leg. I tried to get up, and couldn't stand on it. I had hit my head pretty hard too, and looking back at it, may have had a mild concussion, because it took me a while to figure out what had happened and what was going on.
I got a sled ride down to the clinic, and the doctor had a look at my leg / knee. Right away he diagnosed a torn ACL. My trip with the boys was over before it really started, and I now had to figure out how to get home. Driving down Little Cottonwood Canyon in slippery conditions using only my left leg to operate gas and brakes was not fun. I made it though, and flew home on a red eye that night to a less than sympathetic reception from my heavily pregnant wife. I assured her I'd be fine to continue to help out at home, that I wasn't going to be able to further damage my ACL, and I could delay surgery so I could take care of everything I needed to at home. She held me to it, and I wound up making the half mile each way walk (limp) with my son to pre-school each day for the next week.
I had an appointment with my orthopedic surgeon who was also pretty sure it was a torn ACL. She booked me in for an MRI about a week after the accident, and called me the next day with the results. The good news was my ACL was only partially torn, and I wouldn't need surgery. The bad news was that my MCL was completely torn and I had a tibial plateau fracture. Fortunately, the fracture hadn't displaced, so no surgery was required, but I needed to keep weight off it as there was a risk of it being a much worse injury if something moved. Good thing I'd been walking all over the place on it on the snow and ice covered, pot hole filled streets of New York for a week!
After six months of physical therapy and a ton of gym work, I was back to maybe 90%. The amount of muscle that wasted on the injured leg was shocking. It was probably 18 months to 2 years before my legs looked essentially the same. 5 years later, I have no lingering effects from the accident and I have to consciously think about which leg I injured.