Joint Rotation and Constrain
THE BONE TOOL IS GREAT FOR creating cool armatures that can be easily animated by articulating them. To create more realistic motion, you can control the movement of your armature by constraining its rotation and translation. For example, two bones that are part of an arm could be constrained so that the elbow cannot bend in the wrong direction. You can enable, disable, and constrain the rotation of a bone and its motion along the X-or Y-axis. When X-or Y-axis motion is enabled, a bone can move along the X-or Y-axis to an unlimited degree, and the length of the parent bone changes to accommodate the motion.