The combination of Parameter Wiring, Manipulators, visual Max script and other user defined controls lets users create complete, interdependent systems of animation in 3ds max, without needing to be a coder. Along with improved IK comes a new approach to bones. In 3ds max 4, bones are parametric, geometric objects. That is to say, bones have geometry and parameters that allow you to create a skeleton that corresponds volumetrically to its skin and can be rendered. Interaction with the environment and even other characters can be animated with the skeleton alone, eliminating the need to deform skin in realtime.
Bones are now more a class, or state of objects, as any hierarchy of geometry can be used as bones.
Skeletal hierarchies can also be refined now, breaking any bone in the chain into two or more bones. Squash and Stretch has been added to bones, though combining this with IK requires a lot of set up. The Skin modifier has been improved greatly, to the point where it is a functional Skinning option. This is similar to features in Physique, but much easier to use. Furthermore, while Physique creates parametric deformations, the 3ds max 4 Morph Angle deformer lets you reposition vertices at a given joint angle and drive it as a direct Vertex deformation.