simtk.org

hi all,

I am new to OpenSim and have started processing some data to simulate lower body dynamics. I am particularly interested in the knee joint.

I have used the Rajagopal model. As far as I know, the knee is modeled as a 1D joint that is constrained to allow only flexion and extension. However, in the inverse kinematics results I can see a knee_angle_l_beta value. What does this mean, where can I find more information about it and how is it computed?

I'm curious to hear your advice and I thank you in advance!

Best,
Sergiu

Hi Sergiu,

This coordinate is related to the movement of the patella. If you look into the .osim file and locate this coordinate, you will see that it is actually a coupled coordinate that is a function of the actual knee angle, therefore not a free degree of freedom. Please also note that the knee is not modeled as a pure rotation joint, but it also translates in the anterior-posterior and inferior-superior directions. These translations are also a function of the knee angle. Some links that might help you:

https://simtk-confluence.stanford.edu:8 ... Sim+Models
https://simtk-confluence.stanford.edu/d ... 4%2BModels
https://simtk-confluence.stanford.edu:8 ... Model+2010

Thank you Dimitar for the quick reply and explanation - that is very helpful and much appreciated!