I am calculating the knee joint force during gait. I was wondering is it in "..Bodymodel.Selectedoutput.Right.Leg. JointReactionForce"? Here the JointReactionForce in selectedoutput is not joint reaction force but joint contact force, since the effect of muscle forces is included, am I right?
If so, which coordinate system does the force in? the local coordinate system with thigh? or in global system?
If I want to calculate the contact force, is it \sqrt(Fout[0]^2+Fout[1]^2+Fout[2]^2)?
I also see some articles about calculating the medial and lateral distribution of the knee contact force. Do you know how to calculate it? or do you have some recommend papers?
In the code you have listed for the knee joint the force is measured in the first mentioned frame which is the thigh.kneejoint.
In the selected output the coordinate system used is local wrt to thigh.
Your calculation of the net force is perfectly correct.
I do not have a good paper, essentially it is really just selecting a width and then calculate the force needed to create that torque and add the vertical component to it.
So something in the line of
Latetal /Medial force = 0.5* proximaldistalforce +- moment * 0.5*knee width
1.So the joint reaction force in anybody is actually joint contact force, right? since when only gravity and inertia is computed,then they are reaction forces; and if the effect of muscle forces is included, they are contact forces.
I looked at some reference about calculating Latetal /Medial force, (Richards et al. "Relationship between knee joint contact forces and external knee joint
moments in patients with medial knee osteoarthritis: effects of gait
modifications") .
Therefore, in your formula "Latetal /Medial force = 0.5* proximaldistalforce +- moment * 0.5knee width",
moment is knee adduction moment (KAM), 0.5knee width is moment arm? and it should be "Latetal /Medial force = 0.5* proximaldistalforce +- moment /(0.5*knee width)"?
we only get knee flexion moment from simulation, if we want to get knee adduction moment, is that we need to change the joint type?
another different thing is they use total contact force, and you use proximaldistalforce.
I am confused. Can you help me out?Thanks
I also want to know which represents the total knee contact force. The contact force in the paper is as shown below, but the value in Knee_MedioLateralForce of SelectedOutput is different and has some negative values. Could you tell me where to find the total knee contact force in the chart？Thank you very much.
1: yes the reaction force in AnyBody includes all of it, both gravity, inertia, dynamics, external loads and muscles.
2: sorry but i do not understand how the you end up with "moment/(0.5*knee width)" in the formula this is not a force. your are right about the moment it needs to be the abduction moment is present in the model as a component of the revolute joint of the knee. it has three forces and two moments as reactions.
Let me try to explain a bit more, if the abduction moment is zero the force in the medial and lateral compartments are identical to be 0.5* proximal distal force, if the abduction moment is non-zero it will add or subtract in the compartments depending on the sign of the abduction moment.
The formula from the paper is a moment equilibrium formula, so if the external moment KAM is zero and the CMA_l and CMA_m are the same the KCF_l and KFC_m are equal.
But I still think it should be divided. Because in "Latetal /Medial force = 0.5* proximaldistalforce +- moment / (0.5*knee width)", it is a force formula. and force=moment/moment arm.
By the way, if i use kinematics availbe in Anybody software. can i get the knee width?
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