You can use the HIK leaf roll bone system to add a maximum of five leaf roll bones per limb, giving you greater control over the rotation of your character's upper arms, lower arms, upper legs, and lower legs.
Leaf roll bone controls in the Character Settings tab let you define how you want a character's leaf roll bones to behave as you rotate the character limbs.
To define leaf roll bone behavior
Your character is now selected in the Navigator.
You can map a maximum of five leaf roll bones per limb. All leaf roll bones are parented to the same limb bone. The placement of the leaf bones along the bone and the percentage of rotation per leaf bone is determined by the number of leaf bones per limb. By default, values are assigned to each leaf roll bone in the Roll > Leaf sections in the Character Definition pane. Adjust these values to change the percentage of rotation per roll bone .
For example, if there is a LeafLeft ForeArmRoll1 bone defined, the Leaf Left ForeArm Roll 1 character setting controls the distribution between the left forearm roll and the elbow. Setting the Leaf Left ForeArm Roll 1 slider to 50.0 means that 50% of the left elbow roll will be distributed between the left forearm and the left elbow roll as you rotate the left arm.