**Acknowledgements**

Author WK extends thanks to Ms. Flávia Yázigi for her hard work with the radiography and a long recruitment process. WK also thanks to his mother-in-law, Ms. Sun Lee, for her continuous encouragement for this research. The experimental data used for validation were provided by the "Grand Challenge Competition to Predict *In Vivo* Knee Loads" as part of the Symbiosis project funded by the US National Institutes of Health via the NIH Roadmap for Medical Research (Grant # U54 GM072970). WK also thanks Dr. Michele Conconi of University of Bologna, for making the videos "The Geometrical Arrangement of Knee Constraints That Makes Natural Motion Possible" available to us.

*Proprioception*
