Positive direction of knee joint moments

Dear AnyBody,

I am now working with AMMR 1.3.1, GaitLowerExtremity model. when we finish running the inverse dynamics analysis and look at the selected output, we have 2 knee joint moments predicted by AnyBody, they are Knee axial moment and knee lateral moment. Can anybody from AnyBody tell me where is the positive direction of each moment?

If I check on the model, the knee joint moment prediction is based on femur coordinate system, so, for example, when the knee axial moment is positive, meaning that this moment is pointing upward along the femur bone, am I right?

If we look at the knee lateral moment, the positive direction of the moment is pointing out to the frontal plane (pointing out to patella), is it also correct?

Thanks for sharing

Kindest Regards
Adhi

Adhi,

if you look at:

Main.Studies.HumanModel.BodyModel.Right.Leg.MomentMeasure.KneeJointReactionMoments

you’ll see:

AnyForceMomentMeasure KneeJointReactionMoments =
{
AnyForceBase &Force = …Jnt.Knee.Constraints.Reaction;
AnyRefFrame &Thighknee = …Seg.Thigh.KneeJoint;
AnyVec3 Mlocal = M*Thighknee.Axes;
};

that means the moments are in the reference frame of the KneeJoint node on the thigh. If you include following code:

Main.Studies.HumanModel.BodyModel.Right.Leg.Seg.Thigh.KneeJoint = {
AnyDrawRefFrame drw = {};
};

you’ll see the direction of the x and y axis. Right hand rule and you’ll see the axial knee moment around the y axis (Mlocal[1]) and the lateral knee moment around the x axis (Mlocal[0]):

  /// Internal positive
  AnyVar Knee_AxialMoment = ....Right.Leg.MomentMeasure.KneeJointReactionMoments.Mlocal[1];
  /// Internal positive
  AnyVar Knee_LateralMoment = ....Right.Leg.MomentMeasure.KneeJointReactionMoments.Mlocal[0];
  // Thigh.KneeJoint ref
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