simtk.org

Hello OpenSim users,

I am fairly new to OpenSim and I am trying to simulate the surgical change to the hip joint center location from surgery but when I move the HJC, the femur and muscles move with it. Is there a way to move the HJC location alone, and leave the muscle attachment where it is? This is a common approach during total hip replacement to increase the abductor moment-arm so I would like to consider this in my modelling approach.

Really appreciate your feedback on this and any advice you may have.

Thanks.

Hi,

Take a look at the Frame subsection, where the definition of a custom joint is explained:

https://simtk.org/api_docs/opensim/api_ ... edaudience

In essence you will have to change both the location in the parent and child frame so that the joint is defined correctly. This will keep the body frame properly positioned so that everything defined with respect to this frame will be in the same location.