Knee joint contact loads using Joint reaction analysis

[Zakia Hussain]

Hi everyone

I intend to find the knee joint contact loads using the Joint Reaction analysis tool in Opensim 4.3. I have obtained the muscle forces using CEINMS hybrid model.

I obtained the reserve actuators file from running the MATLAB script createActuatorsFile.m file included in the resources folder. Not really sure if I am correct. I have included all the files here

stw1.rar

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.

However, when i run the JRA tool i get unrealistic results as in figure 1
. These results are same even if i change the forces file here or the actuators. Its always the same.

Also, the messages window in OpenSim shows

Found 60 actuator forces with time stamps ranging from 2.19to 4.85.
The forces file does not contain enough actuators.
Actuator forces will be constructed from the states.
Printing results of investigation 65 to C:\Users\DELL\...


Also, i have 3 separate externalload.xml files since, i have 3 force plates and want to consider foot contacts with all so I repeat the JRA analysis 3 times with 3 different external load files.. Can this be a problem?

Any help would be much appreciated.


Regards
Zakia

[Mohammadreza Rezaie]

Hi, some possibilities:

• there is no stw1.mot file (GRF) for external load files (<datafile>stw1.mot</datafile>) in your attached files.

• in ID_external_loads_1.xml file, identical identifiers were assigned to both feet (e.g. ground_force1_v).

• the actuators have no data (force or activation).

Please double-check these settings.

[Zakia Hussain]

Hello

Thanks a lot for your response. I am including the stw.mot file

stw1.zip

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.

I am analyzing the sit-to-walk motion so the first ID_external_loads_1.xml indicates the phase when the person is seated on the chair as such both feet are on the first force plate.

ID_external_loads_2.xml

ID_external_loads_2.xml

(2.36 KiB) Downloaded 10 times

(attached in this reply) indicates the phases when the subject gets up and moves his stepping leg to 2nd force plate while the other leg is still on the first FP.

ID_external_loads_3.xml

ID_external_loads_3.xml

(2.36 KiB) Downloaded 8 times

indicates when the leg on FP1 moves on to FP3 while the stepping leg is still on FP2.

the actuators have no data (force or activation).

This is my confusion, I am not sure how we assign values to that. I tried using the cmc_actuators.xml

cmc_actuators.xml

(9.92 KiB) Downloaded 12 times

file (included hr) which comes with the Rajagopal model but it didn't change my results.


Any suggestions would be highly appreciated.

Thanks again

[Mohammadreza Rezaie]

Hi, thanks for the files.

Try this one: First, remove the actuator file from the JRA setting,

The forces file does not contain enough actuators

Also, these muscles do not exist in your force file, so remove these muscles from the model.
ercspn_r ercspn_l intobl_r intobl_l extobl_r extobl_l

Let me know how it works.

Best
Mohammadreza

[Zakia Hussain]

Hello
i did as you recommended. Not sure if they are realistic but atleast better than what I have getting before.

I did the JRA in two settings by disabling/enabling the ligaments respectively. The results show drastic difference.



Do you have anymore recommendations to improve my results..

Incredibly grateful for your insightful suggestions

[Mohammadreza Rezaie]

Hi, I'm not sure if ligaments are going to be used in your workflow, but if you remove them entirely, you will get smooth curves. JointReaction analysis is actually quite sensitive to input parameters.

[Zakia Hussain]

Yes I will remove them.

Thanks for your help