Interactive visual and force rendering of human-knee dynamics

Abstract

The kinematics and force/displacement relationships of elements of biological joints are notoriously difficult to understand. In particular, the human knee has bearing sur- faces of complex geometry that are connected by interacting sets of compliant tissues. It is proposed that knee motion and reaction forces can be usefully presented, during virtual manipulation of the joint, by simultaneous visual and haptic rendering. A pro- totype system for visuo-haptic rendering of the human knee included an extension of a common model of knee motion, a solution of the extended inverse kinematics, and an approach to the computation of bearing-surface reaction forces which balances the two needs of speed and accuracy. Knee kinematics were rendered with a graphical animation, and constraint forces were rendered with a haptic interface. A two-degree-of-freedomplanar haptic interface detected the position of a handle and applied forces via the handle to the human opera- tor. Multimodal presentation of motion and forces is a promising technique for studying ligament balancing and reconstruction, and may also be useful in studying implantation of artifical joint components. 1