The model "goes crazy" after adding new DoFs

[Alexandra Yurova]

Dear all,

i added some DoFs to patellofemoral joint in knee model https://simtk.org/projects/kneemodel, i.e. defined additional coordinates, specified the range and defined new spatial transforms as linear function of the corresponding coordinates or as simsplines.

The results of Forward Dynamics demonstrate abnormal patella movement, which significantly declines from expected trajectory.

How one can fix this and achieve normal trajectory of patella?

Regards,
Alexandra

[Vinay Kumar]

Hi Alexandra,

The forward simulation doesn't follow coordinate limits as such.
I will suggest you to add a coordinate limit force (https://simtk.org/api_docs/opensim/api_ ... Force.html)

-Vinay

[Alexandra Yurova]

Hi Vinay,

thank you for your response!

Is there any way to add coordinate limit force using .osim file? I am working using GUI.

Is this kind of solution actually physiological?
I tried to vary some model parameters to avoid additional constraints, but couldn't obtain any reasonable result. I don't know, if there is any strategy for this...

Thanks,
Alexandra