Knuckles the Echidna figure is no clone of the normal 3-inch line. He has goggles, special gloves and 'Riders style' shoes. And he ofcourse comes with a Sonic Riders board. He has 12 points of articulation. 

Photo by BombermanWinner

With these in-box photos, you can see the size comparison for the figures. Storm is nice & big, as he should be (look where his head & feet are in the box) The boxes all have good smooth bubbles, & the figures attempt to be posed somewhat dynamically, so leaving them MIB isn't bad. Each figure has about 12 points of articulation, and as you'll note here, Tails & Knuckles have their 'Riders style' new shoes & slightly special gloves. They also have their goggles from the game, and come with rolling boards.