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Joint Reaction Analysis + Moco?
Posted: Thu Apr 14, 2022 11:28 am
by maddiegrosklos
New Moco user here!
I designing a study for my PhD and would love to use MocoTrack and MocoSolve to answer my questions. However, a key element of the hypotheses involves changing joint contact forces with altered muscle strengths. I cannot find any information on if I am able to compute something like the joint reaction analysis tool (in OpenSim) in Moco.
It is imperative that I am calculating and reporting the compressive forces at the joint, and not just the net torques.
Thanks in advance
Re: Joint Reaction Analysis + Moco?
Posted: Fri Apr 15, 2022 2:50 am
by pvb
Hi Madeline,
I posted some matlab code that computes the JointReactions from a converged solution in moco a while back. That was for a previous version of moco. I just posted a new version of that script, since I'd made the required changes after updating anyway. The code is in
this thread.
There was also recently a
discussion on the forum about what the JointReactions actually represent.
Cheers,
Pasha
Re: Joint Reaction Analysis + Moco?
Posted: Sat Apr 16, 2022 6:49 am
by maddiegrosklos
Thank you Pasha,
This is perfect. It will be a while until I am able to apply it to my data, but with this I can confidently defend my methods in my upcoming candidacy proposal.
The thread on JointReactions was also insightful. Such a tangled web of a topic and a great conversation about it!
Best,
Madeline
Re: Joint Reaction Analysis + Moco?
Posted: Wed Apr 20, 2022 7:24 am
by maddiegrosklos
Hi Pasha,
I am explicitly interested in the anterior hip JointReactions, and was wondering if I am able to define parent and child bodies to ensure that I am looking at just the anterior region and not the entire joint.
I hope this is not a silly question. I am assuming it is possible but wanted to ask someone with more experience.
Best,
Maddie
Re: Joint Reaction Analysis + Moco?
Posted: Wed Apr 20, 2022 12:48 pm
by nbianco
Hi Madeline,
It's not possible to "split up" the joint reactions between anterior/posterior segments of a joint. There's only one set of 3D forces and moments based on the definition of a joint.
One approach would be to create a hip model with multiple compartments,
similar to Zach Lerner's knee model. If there's any relationships between hip moments and compartment forces, that could be used to create a the MocoGoal that you need.
-Nick
Re: Joint Reaction Analysis + Moco?
Posted: Wed Apr 20, 2022 1:43 pm
by maddiegrosklos
Thanks Nick,
Your response made me realize I was thinking about it wrong. I will be able to determine when the joint force is anteriorly directed on the acetabulum and that will be good enough for my application.
Maddie