Use parameters at the Link sub-object level to change how deformation around joints occurs. When a joint in the skeleton bends or rotates, Physique, by default, deforms vertices uniformly on either side of a joint. You can change these defaults by using the tools at the Link sub-object level. For example, you can adjust the amount of skin sliding that occurs along a limb as the limb bends, or change the angle of the crease between the upper arm and chest.
The Physique Deformation Spline
The deformation spline displays as a yellow curve that runs through the mesh.
Like a spline object, the deformation spline created by Physique is a continuous curve through several points. While a spline object runs continuously from vertex to vertex, the deformation spline is a smooth curve running from joint to joint. The Bend, Bias, and Tension spinners can change the shape of the curve, much as you can rotate or scale the handles at a spline vertex.
The deformation spline also takes into consideration twisting and scaling of the skeleton’s links. At the Link sub-object level, you take control of the behavior of the deformation spline, and subsequently gain full control of the skin’s behavior relative to the skeleton’s movement.
Controls on the Link Settings rollout let you adjust the behavior of the selected link.
When a joint bends, the skin can "collide." Without collision detection, it can overlap unrealistically. This is especially likely when one or both of the links have bulges. The joint intersection controls can detect skin collisions and correct overlap by creasing the skin.