Minifigures don't have knuckles per se, but with this custom LEGO weapon they can have spiky ones. The Cestus is great for all those gladiator minifigs looking for an edge. Don't just take our word for it! Here is a fan review from Brock Eckstein:

A VERY fine product. I have been wanting a simple set of spiked or brass knuckles forever and this is perfect!

Thanks Brock! Get this awesome custom LEGO weapon and create a goblin gladiator like the one below who is also wearing a Goblin Helmet.