simtk.org

Hi,

I typically use ID tool for calculating internal knee joint moment and do a cross product to determine to external knee joint moment. I have read in a few publications that the opensim's ID analysis can be used to calculate the external knee joint moment. Can anyone please advise on how one can do ID tool to calculate the external knee joint moment? Thanks!

Hi, just to clarify - meant I am referring to the frontal plane.
Hope to hear from someone on this.

Your external moment (cross product of ground reaction force and position vector) sounds like a quasi-static analysis. This can be a good approximation for the joint loading, but it neglects the inertial and gravitational effects on the body segments between the joint and the ground.

If you included those effects correctly in the external joint moment calculation, you would get an external moment that is exactly equal and opposite to the internal moment that OpenSim provides.

Here is a recent reference on the ISB recommendations for joint moment terminology and reporting:

Derrick et al. (2020) ISB recommendations on the reporting of intersegmental forces and moments during human motion analysis. J Biomech 99:109533.

Ton van den Bogert