|Manga Debut||Chapter 94|
|Anime Debut||Episode 41|
The Metal Knee is a metal knee attached to Lussuria's left knee, primarily used as a weapon to enhance his already formidable Muay Thai skills. It is capable of doing damage, but it can also deal an even greater amount of damage if struck with force, thus attacking through defending. It is also able to temporarily stun to a certain degree, as seen during the Sun Ring Battle: when Ryohei punched Lussuria's Metal Knee with his left arm, he wasn't able to use it for the rest of the fight. It was, however, successfully destroyed by Ryohei's fully charged Maximum Cannon.