Here is a large size modern Knuckles plush.
He's offical, but he's also somewhat run-down. The tag you can see is still on him, but it's all in Chinese so you can't read it anyway. The fabric of his shoes didn't stand the test of time very well at all. It was that 'plasti-coated' fabric which has a shiny or leathery look. However, that stuff isn't always stable, even in ideal conditions, and here you can see that it is mostly disintigrated and likely made a huge mess in someone's house.
But the rest of the doll is just fine (naturally) the fists are pretty big, chest stripe is good, expression seems normal & the legs are long enough. He would be a good collectible, if not for the poor fabric of the shoes.