high joint moments after Inverse Dynamics

[Christian Greve]

Dear OpenSim community,

I am using a multi-segement foot model for inverse dynamic analyses. I follow the standard OpenSim workflows of Scaling RRA and IK. When performing inverse dynamic analysis there are very high joint moments at the mid-tarsal joints (1-2 times body weight) even in the absence of ground reaction forces (during swing).

The ankle and subtalar joint moments are within a physiological ranges and approach zero during swing.

Do you have any suggestion what the underlying cause of these high joint moments at the "small" foot joints might be? There are no dynamic inconsistencies and the kinematics look normal (e.g. no spikes or excessive joint positions).

Thanks for your time

Christian

[Mohammadreza Rezaie]

Hi, multi-segment foot kinetics is a controversial topic. Many researchers use inverse dynamics to calculate it similarly to any other joint, while a few believe this output could not be trusted. A force plate measures the force on the whole foot, and we don't know the force on each segment. So, it is likely not handled correctly in the inverse dynamics.

However, 1-2 times the body weight is so huge, and there might be a modelling issue. Could you share your model, experimental, and setup files? Then, I will check.