It sounds like you might be thinking of a different Sonic game, or perhaps a fan-made game. To help me figure out what you're asking, could you tell me:
* What platform are you playing on? (e.g. PC, Sega Genesis, etc.)
* Do you have any screenshots or video of the game?
* Is it a specific game with a name, or is it a fan-made game?
Once I have a better idea of what game you're talking about, I can tell you how to punch with knuckles in that game!