AC Milan midfielder Gennaro Gattuso has long been considered one of the hardest men in football, and we now have scientific proof of that fact.

During surgery on his knee this week, doctors had to switch scalpels to get a sharper blade.

"Gattuso's bones are very hard. It's extraordinary," said Krystel De Reycke, who assisted in the operation in Antwerp.

"We could not break them. It's the first time it has happened to us."