observing the sagittal knee joint torque

Main Forum
1

Good morning. I am currently observing the knee with the following model.
(Since we created the motion separately, please
do not proceed with “MotionAndParameterOptimizationModel”.)

In order to observe the sagittal knee joint torque I am looking following path.

Main.Studies.InverseDynamicStudy.Output.BodyModel. *(Left or Right). Leg.Jnt.Knee.Constraints.Reaction.RefFrameOutput.M [0] [2]

But the patterns and values are strange.

I doubt the following, but I do not know the exact answer.

  • Is there a problem with the Joint drivers?
  • Is the moment in the y direction (M [0] [1]) is sagittal torque??
  • Is the above path inadequate to observe Joint Torque?

I will be waiting for your reply.
Always Thank you.

2

Hi

I have been unable to run the model i think you have modified the forceplate class and provided it.

The property you are looking at is the moment in the reference frame , measured in global. I think you will also see that the two moments have the same values but differences in signs.

Best regards
Søren

3

I’m really sorry.
So I attached other file using real data.

You mean that the sagittal moment will be M [0] [0] (on the x-axis moment), because it use grobal coordinate.
But I think this result is too small.
Therefore, I think there is a problem with my model.

And the following path is different from the joint torque?
Main.Studies.InverseDynamicStudy.Output.BodyModel.Right.Leg.MomentMeasure.KneeNetMomentMuscle.M (or Mlocal)

Sorry to trouble you.
Thank you.

4

Hi

I have tested the model and it gives a max moment of 37Nm in the knee running with no muscles…

The moment has six components.

Ref frame 1 : Mx,My Mz global
Ref frame 2 : Mx,My Mz global

Please have a look in the book “Dynamics of Human Gait” by Christopher L Vaughan, for a good references on actual values.

Best regards
Søren

5

Thank you for your reply.
I’m sorry, but I would like to ask you once more that it confused.

Where can I get the value of 37Nm?
The reaction moment (Main.Studies.InverseDynamicStudy.Output.BodyModel.Right.Leg.Jnt.Knee.Constraints.Reaction.RefFrameOutput.M) of the knee shows that the maximum value in the sagittal direction is -2.66Nm and the maximum value in the coronal direction is 15.8Nm.

Where can I get the value of 37Nm and what is the direction?

6

The 37Nm applies to the left leg, you are correct about the right knee it was about 15 Nm

7

I checked both the moment of the left leg and the book that you informed.
But still questions remain.

37 Nm means moment of coronal (adduction) direction.
The moments of sagittal direction(flexion/extension) are still very small.

In that book, Sagittal and Coronal moments are not much different.

So I wander why the result of this model is wrong.

8

Ok now i understand the question.

The moments you are looking at in the joint are the reaction moments in the revolute joint. So these moments do not represent the flexion extenstion because this moment is the only free DOF in this joint. So you will not see any reaction relating to flextion extension if this is what you are looking for.

This model has no real muscles, so in in this model there are some joint muscles which carries the applied loads, please look at the JointMuscles folder in the leg model, it will have two muscle for each dof one in positive direction and one in negative dirction.

Best regards
Søren

9

Is that what you mean? I found it.
Really thank you so much. :smiley:

10

yes :wink:

Best regards
Søren