IS knee varus/valgus in this case? Or rotation?
> discussed previously on biomch-L by Grood vs. our fellow Dutchman Herman > Woltring, so no need to repeat it here. I vote for Woltring though. I agree. In the knee the two minor cardanic rotations are so sensitive to the choice of rotation order and coordinate system that they become almost meaningless. The knee joint is definitely a case for the Woltring representation. You still have the crosstalk problem though, if you use Woltrings “helical angles”. There is one large one and two small ones. The small ones are sensitive to small rotations of the segment coordinate system. A better representation would be: magnitude of the rotation and orientation of the axis. The orientation could be expressed as azimuth and elevation relative to a certain coordinate frame.
