FDK with bone and cartilage

A model consists of a joint with four meshes, two bone and two cartilage meshes, and some ligaments.
How do I assure that during FDK the cartilage does not move independently of its bone?

The following contacts are defined, as described here:
Nolte et al. - Development of a patient-specific musculoskeletal model of a healthy knee to analyze hard and soft tissue loading (2013)

Cartilage1 - Cartilage2

Bone1 - Bone2
Bone2 - Bone1

Bone1 - Cartilage2
Bone2 - Cartilage1

Thank you


I assume you mean the contact between the Meniscus to the Tibia and articular cartilage to Femur?

It’s up to you to decide whether the cartilage is allowed to move independently.

If you want to allow it to move independently, you can define “how much” using a spring stiffness function.

If not, you can fix it to the bones using ‘Hard’ constraints(not using FDK).

Best regards
Kasper Pihl Rasmussen

It’s a different joint.

But IMO, if the movement of the bones is force dependent, the cartilage of each bone should move with its bone.

OK, Constraint type of the cartilage has to be “hard”.

But how do I link the movement of the cartilage with the force dependent movement of the bone?

Should the Kinematic Measure of the driver of the cartilage point to the kinematic measure of the bone?

Thank you

Cartilage that is attached to a bone should move together to some extent, yes, but the movement there IS between bone and cartilage should be defined using a spring stiffness function. You would have to find the spring function to determine that.

Remember that the CType you define can either be ForceDep(FDK) or Hard/Soft(default kinematics).

I will point you to our tutorialwhere it is explained with an example using two bones, but the same principle applies in more complex cases with several cartilage segments between bones.

I hope it helps. It is a bit difficult to help with so little information.

Best regards,
Kasper Pihl Rasmussen

1 Like