Joint Moments

[Evgeniya Tomskaya]

Hi!
We have some problems with joint moments calculation.

Early we used Visual3d and we have a knee flexion moment value from - 30 to 200 Nm and smooth chart.

Now we use OpenSim. After running Inverse Dynamics tool, we have knee_angle_r_moment with values from -200 to +50. And our chart has a lot of fluctuations. We attach example of chart.

Questions :
1) What formula Opensim use for calculation Knee angle moment?
2) What difference is between knee_angle_r_moment (that we have after Inverse Dynamics tool) and knee_r_on_tibia_r_in_ground_mx (after Joint reaction analyze tool) ?

Thanks

[Thomas Uchida]

1) What formula Opensim use for calculation Knee angle moment?

Please see the documentation on the Inverse Dynamics Tool (http://simtk-confluence.stanford.edu:80 ... e+Dynamics), particularly the "How Inverse Dynamics Works" page (http://simtk-confluence.stanford.edu:80 ... mics+Works). The "Best Practices and Troubleshooting" section on the "Getting Started with Inverse Dynamics" page (http://simtk-confluence.stanford.edu:80 ... e+Dynamics) recommends filtering to reduce noise in the results.

2) What difference is between knee_angle_r_moment (that we have after Inverse Dynamics tool) and knee_r_on_tibia_r_in_ground_mx (after Joint reaction analyze tool) ?

Joint reactions can be expressed in any frame; it looks like you have configured the tool to resolve in the frame fixed to ground ("…in_ground…"). Please see the "Joint Reactions Analysis" page in the documentation: http://simtk-confluence.stanford.edu:80 ... s+Analysis.