Al, 4 y.o., scared me at the end of Day 6 on a 9-day wilderness backacking trip in a very remote area. All of a sudden he was limping severely, foreleg. We'd had a typical day, moderately hard, well over 12 miles with considerable up-and-down steep terrain, all on trail. We stopped, and he snoozed and dithered for maybe an hour while I set up camp. Then he would not follow me when I went to get water, even when I insisted stridently. That's when I spotted the limp. He wasn't just favoring the leg, he wasn't even walking! We were a LONG ways from the nearest road! It looked like it might be a serious situation. No detectable paw injury; I feared a joint problem. Quite a bit later, after dinner, he seemed normal again. I put the Pawz booties on his front feet next day, but they didn't last the day, or I removed them. I saw no evidence of limping on the last 3 days of the trip. He was fine.
Don't know what it was. No thorny plants or broken glass there. No visible wound. You know how you sometimes get a momentary crick, or your leg cramps, or goes to sleep, or a minor owie really stiffens up when you stop and rest? Whatever it was, it was dramatic but ephemeral.