There would be chance that when youre fighting some player and you dont have any protective gloves on (s)he will cut few of your fingers off. If you lose certain fingers you cant use certain weapons anymore. For example if archers get some of their fingers cut off, they cant shoot anymore. And if you lose your thumb you cant use swords/battleaxes anymore. Or then their damage would be reduced. You could also get these (permanent) injuries from very big and dangerous animals. Such as bears.
Chance for this to happen would be quite small.
And generally idea that you can lose some parts of your body, especially in swordfights.