I have never felt leg pain like I felt after a friend and I did a four-day, 75ish kilometre tramp (that would be a 'hike' in American, 'cept with more rain ). The worst part was the walk back to town after we'd finished the track proper. Ow ow ow! I was hobbling for days afterwards! My knee was a little sore, but it was mostly muscle pain; I think there must have been several litres of lactic acid in each of my quads alone...