[Lowlimbmodel09-news] New version: important modification to patella joint

[Edith Arnold]

Hi Lower Limb Model Subscribers,

I've added an updated version of the lower limb model to the downloads
page that includes an important modification to the patella joint to
correct for a bug in some versions of the scale tool.  In forum
message 4428* I described a problem that occurs when scaling
translational coordinate coupler constraints in OpenSim and a work
around that involves changing the model file.  It appears that this is
still an issue in some versions of OpenSim, but it can be avoided by
using only rotational coupler constraints.  To that end, my colleague
Samuel Hamner has modified the model so that the patellar motion is
described as a function of a temporary coordinate, knee_angle_beta,
which is then coupled to knee_angle.  This reduces the number of
coordinate coupler constraints from 6 to 2.  This new version includes
"v2" in the model name, so it should be clear in the gui which model
you are using.

Sam has also combined the lower limb model with his running model that
includes arms, to make a full body model, and given me permission to
add it to this project.  If you use this model with arms, be sure to
cite both the lower limb model paper and his running paper.**

As always, complete details are included in the .osim file under the
<publications> tag and are viewable in the GUI by right clicking the
model name in the navigator and selecting "Info".  Please let me know
if you have any questions via email or in the project forum
(https://simtk.org/forum/?group_id=468).

Best Regards,
Edith Arnold
PhD Candidate
Neuromuscular Biomechanics Lab
Stanford University


* https://simtk.org/forum/message.php?msg_id=4428
** Arnold, E.M., Ward, S.R., Lieber, R. L., and Delp, S.L., A model of
the lower limb for analysis of human movement, Annals Biomedical
Engineering 2010 Feb;38(2):269-79. Epub 2009 Dec 3. (2010)
Hamner, SR, Seth, A, and Delp, SL, Muscle contributions to propulsion
and support during running. Journal of Biomechanics,
doi:10.1016/j.jbiomech.2010.06.025 (2010)