Standard Standing Model

Main Forum
1

I noticed that there is a small moment in the frontal plane in the knee of the standard standing model. I was wondering if this is due to you modeling the phenomenon that the medial condyles of the knee experience higher load than the lateral.

2

Hi Parady,

This model has the feet’s glued to the ground.
Since the knee is a revolute joint it has no cost to add a moment to frontal plane. The model will try its best to lower the muscle activations by making active use of the boundary conditions available and this may be the reason for it to add this moment. In other words it may reduce a muscle activation by making active use of this knee moment.

Best regards
Søren

3

Hi Søren,

thanks for the explanation, that is quite interesting. I’ll have to think about how to evaluate this phenomenon with regard to the human anatomy with a non-ideal 6 DOF knee joint.

Regards,

Patrick

4

So I looked into this question a bit further and it seems like the muscle activation can not explain why there is a higher moment in the knee frontal plane for the standard model than for modified hip and knee ab-/adduction angles.
You can find the 3d plot of the moments here:
http://youtu.be/uhyNnMX8zxk
And the muscle activations can be found here:
http://youtu.be/BL74pQiBqBM

As you can (hopefully) see the muscle activation is declining like the moment. Its very great for the standard posture.

5

Has anyone validated the model in some way?

And do you have any ideas regarding my previous post?

6

Hi Patrick,

validation was made, but for the standard knee with the revolute joint I’m afraid that the validation was not that detailed.

In your first graph is an error, or? It is the Knee and not the Hip moment, or?

Did you use the standard standing model, or including ground reaction forces?

The graphs are hard to read, where was the point of a 0Nm moment?

7

Hi Amir,

I was talking about the knee joint moment, sorry for the mess. The label in the video were incorrect.
The angles in the joints are plus and minus around the standard angles of the standing model.
Here are two figures with a better view:


Regards,

Patrick

8

Patrick,

I get it now.

Are you using the moment form the constraints, or the one form the selected output?

9

Hi Amir,

this is the Leg.MomentMeasure.KneeJointReactionMoments.Mlocal[0] displayed.

Patrick

10

Hi,

is there any new input concerning my inquiry?

Best regards

Patrick

11

Hi patrick,

I looked into what Søren suggested and run the models with cond contact. This actually decreased the moment, but the effect is still the same.
I’m looking currently little bit into the knee anatomy…
Sorry, no good news yet.