Board Thread:General Discussion/@comment-24074103-20131204160455/@comment-2061959-20140727002219

One of Knuckles' moves in Sonic Battle involved causing rocks to fall from the sky via "supernatural control of the earth". Plus his healing and stuff in the game was also explained as channeling elemental earth energies or something.

So, Knuckles is in fact an earthbender. An earthbender with the strength to shatter a stone boulder with one punch. And also an earthbender that has been given fire-based skills.

Since, according to Avatar: The Legend of Korra at least, Lavabending is just a sub-form of Earthbending, it would make since if Knuckles was able to simulate pyrokinetic abilities by harnessing the geothermic power of molten rock, combined with the force, friction and intensity of his punches to create devistatingly powerful fire-based attacks and stuff.

Basically, earthpowers can be used for firepowers or something and this may apply to Knuckles.