I think, the MK I and MK II are basically the same excluding some minor details (ARM,HELMET), so i thing the legs/knee piece would be the same
The Picture of the SPARTAN III (Kurt) lying down in front of the elite, is just fan art so the arm pieces are wrong.
But, i must admit they are pretty cool, still i prefer the MKII ones.
Actually to clear things up why don't we 'spot' the differences between the two armor types and make a list