Sonic & Knuckles is a 1994 side-scrolling platform video game developed by Sonic Team and published by Sega for the Sega Genesis.
Definition #2 for "knuckles 2"
Knuckles is a character from the Sonic the Hedgehog franchise. He is an echidna. After appearing as an antagonist to Sonic and Tails in 1994?s Sonic the Hedgehog 3, Knuckles eventually became a recurring character in the Sonic franchise and has been the subject of several memes, including the & Knuckles series and Knuckles Sings.