So I'm coming down High Hrothgar, just riding down and leaving Lydia in the dust. I get to the frost troll (which I just rode past on the way up) and decide to kill it. Warcry to disable it for a time, I get it down to 1/3 hitpoints and it regains its senses. Lydia conveniently shows up, distracting it so I can finish it off... but not before the troll pounds her into the ground. I think she may have taken a FUS in the process, as well. So she's crawling on the ground, and I figure she's recovering. So I run down the mountain, taking the cliff shortcut, and head to Vilmeyr... it was friggin' COLD outside (Frostfall).
I didn't notice that Lydia hadn't caught up to me. I just eventually went to bed (too much bad weather to head back down the mountain), and when I woke up, there's Lydia, finally caught up... and still crawling. lol