RRA and CMC Knee Moment Differences

[Cailin Rice]

Hi all,

I am analyzing Achilles and Patella tendon loads during running under different running conditions. I am comparing processed experimental data to simulated/estimated data from an OpenSim processing pipleline I have developed. The pipeline uses a variety of musculoskeletal models derived from a generic model (Hamner et. al. (2010) Full Body Running Model) and conducts analysis on a number of strides in the running movement. The derived models each have a patella bone, as well as 1 DOF knee joint movement defined by Walker et al. (1988), the rest of the model is the same as Hamner et al. (2010).

The pipleline process follows: Scaling -> IK -> RRA -> CMC + Muscle Analysis.

The issue I have is with the RRA and CMC joint moments, specifically the knee moment (See attached graph). The RRA functionality in the pipeline runs until there are no "bad" results (as per the documentation). The majority of the joint moments seem fine, and the RRA vs CMC kinematics results also are good (other figure), however the knee moment is drastically different.

If anyone has an idea of what could cause this, please share?

[Cailin Rice]

Hi All,

Since it is a little bit urgent for me, I would be very grateful if one of the OpenSim developers or someone who knows the OpenSim in advance can help me or guide to get the answer. Is it because the optimization target functions taken by the RRA and CMC tools differ? Or is it possible that the optimization targets for the CMC tool are stuck at a local min/max?

Sincerely,
Cailin