WRT the Battle of Visby, I remember reading about the wounds inflicted, but for the life of me, I can't dig it up right now.
Anyway, here's something interesting from John Keegan's A History of Warfare...
One of the most gruesome discoveries made at the disinterment of the mass grave on Gotland, containing 2000 bodies from the battle of Visby of 1361, was that many of the dead had been extensively mutilated--typically by repeated sword-cuts down their shins--and such cuts could only have been inflicted after they were disabled. (p121)
I wonder if this ritual mutilation skewed the data somewhat?
That's not to say that the legs weren't prime targets however.
The legs were especially vulnerable in the earlier Viking period (10th c. or so), when leg armour was non-existent (being foregone in the interest of mobility--amongst other reasons) and the round shield was used in preference to the even earlier oval shield, or the later kite.
The sagas are filled with stories of men's legs being sheared off, which is one reason they practiced the "salmon leap"--the best defense against a blow is to not get hit by it!