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)
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.