Was bombing it down some bullet-proof hardpack, and caught and edge. Did a couple of back flips, and I may have blacked out for a second or two, but I can't remember. A total beginner mistake, but I probably shouldn't have gone out with a cold.
Damaged meniscus in the right knee.
Damaged ligaments in the part that connects the ribs to the spine.
Something weird on my left ankle that the doctor reckoned was a sprain.
I did this on December 22nd, and lost about 40 days of riding. Couldn't walk for about a week, and had a slow recover over the subsequent 4 weeks. Am back to riding twice a week, but feel kinda sore. I'm sooooooo glad I was wearing a helmet. I'm now riding with body armour.