[Eye of Sarnath]

Well, look at it this way. Now, suppose they decied to put ball joints at the knees. The Turtles have the pads on their knees, and how would you then put pads on top of a ball joint? Realistically, how would you do it? There are ways to do it, but it would be difficult, and, in the end, not really worth it. The Turtles are pyhsically different from humans, and this doubtless effects where thy decide to add articulation.