The Leap Motion controller tracks the forearm attached to each hand. Although much of a forearm is typically outside the Leap Motion field of view, the controller bases length and elbow position on the size of the hand and the portion of the forearm that is in view.

In the LeapJS JavaScript API, the properties of a forearm are represented by the Bone class (there is no separate Arm class). The arm properties include the width, length, position and orientation of the arm. Although a physical arm contains two physical bones, the skeleton model only contains a single bone for the forearm.

Get the Bone object representing the forearm using the Hand.arm property.