simtk.org

Hello,

I'm looking for a way to calculate the contribution of each muscle (or group of muscles) to joint contact force. How to decompose joint contact force (calculated through JRA tool) into its muscle and intersegmental force components?

Any help is much appreciated.

Regards,
Mohammdreza

Hi,

I have a similar query too.

My second question is :
Can the knee joint contact force estimated through JRA be considered as the total knee joint load (since its the total reaction load at the joint)?


Thank you

Regards
Zakia

Hi, I see the inconsistency in terminology. You can consider the output of JRA tool as total joint contact force and compare it with the experimental forces measured using an instrumented total knee replacement.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3319529/

Back to the topic, I found that this plugin extracts the unit vectors of muscles' line of action.
https://simtk.org/projects/force_direction
So, the rest of the calculations will be easy (I will try).

Mohammadreza

Thank you so much for your response. I will definitely go through this article.

Incase of this plugin do share your experience hr.

One more thing, when you find muscle forces through CEINMS one of the output.sto file is the muscle contribution that might be helpful i guess.

Thanks again

Hi,
I have tried the following approach.

I rewrite the data in "Results_StaticOptimization_force.sto" putting zeroes everywhere except for the muscle under study. At the same time I also zero the external loads so the GRF is zero. Then I run the JRF analysis with one muscle "ON" and repeat this for each muscle I am interrested in.

I would be grateful for any ideas why this IS or IS NOT a good way to analyse the contributions.

Best regards, Martin

Hi, this should work. Joint contact force would be the sum of intersegmental and muscles forces. I would suggest you calculate the intersegmental force using JRA tool and subtract it from your joint contact force calculated by isolated muscle(s). If you exclude the GRF, there are still other forces acting on the joint and contributing as intersegmental force, such as weight, gravitational, ..., and inertial forces.