Ligament bending

[Sebastian Urbanowski]

Dear community of simtk,
I have problem with LCL and MCL unphisiological bending. I runned simulation of knee bending in febio. The ligaments were bended in wrong way. I checked material mode, and its fine. What should i do to fix it?
I will be really greatfull for help.

Best Regards,
Sebastian

[Ahmet Erdemir]

Hi Sebastian,

Can you clarify what you mean by unphysiological bending of LCL and MCL? Are they penetrating the bone surface? If so, this can be resolved by activating contact between these ligaments and bones.

Ahmet

[Sebastian Urbanowski]

Hi Ahmet,
The ligaments are penetrating the bone as you said. But it's not a problem. The main issue is extra bending. If I think correctly the LCL and MCL should were shorten when knee is bending. In my simulation the ligaments are bending when knee is bending.

Best regards,
Sebastian

[Ahmet Erdemir]

The bending that you see is expected as the ligaments have a ground substance with a small but stabilizing modulus (providing compression and bending stiffness). You can set that ground substance to zero to represent a purely tension only ligament material. Yet, the simulation will likely have convergence issues.

Best,
Ahmet