Get same Skeletal Rig movement from 3dsmax to Unity

Hi, everybody!

Suppose I have a humanoid Rigged with a CAT skeletal rig in 3dsmax. When I move its foot bone, for example, the rest of the leg (calf bone and thigh bone) move accordingly to how the foot bone moves.

When I export this to unity, and move the foot bone, It only moves the foot, and the rest of the leg doesent move.

Is it possible to get the same movement for the cat rig ((or any other type of skeletal rig)) (all the leg moving accordingly to how the foot moves) from 3ds max to unity?

What I wish to achieve with this is to animate the character with script, not with animation, wich would let me get realistic foot placement, make the char punch at an extremely precise point, look at another character with its head, etc. Thanks for anybody who can help me!