How the Native Knee Flexes — teaching sequence
Source bone/cartilage geometry: Open Knee(s), specimen oks009, Open Knee(s) Development Team.
https://simtk.org/svn/openknee/oks/oks009/Geometry/
Source license: Creative Commons Attribution-ShareAlike 3.0 Unported.
https://creativecommons.org/licenses/by-sa/3.0/
Derived anatomy.glb and the 4K animation are distributed under CC BY-SA 3.0.
Modifications: welded/smoothed surfaces, mirrored left reference to right knee,
warm ivory materials, cartilage tint, sagittal section geometry, prescribed
0–120-degree medial-pivot motion, illustrative menisci, markers and lecture HUD.
No endorsement by the source authors is implied.

The animation is a prescribed teaching model, not an experimental recording,
patient-specific simulation, or validated joint-contact/meniscal mechanics model.
Numeric targets: medial 1 mm posterior, lateral 20 mm posterior, 20.2 degrees
coupled axial rotation by 120 degrees, with a 55 mm inter-marker distance.
The condylar-center and contact-patch concepts are distinct. Meniscal motion
and the early medial contact shift are illustrative, not measured from oks009.
Sagittal surfaces are sections extracted from the reference bone geometry.
Beyond 120 degrees is not animated.

Clinical sources:
Iwaki H, Pinskerova V, Freeman MAR. 2000. PMID 11132285.
Hill PF et al. 2000. PMID 11132286.
Johal P et al. 2005. PMID 15598453.
Freeman MAR, Pinskerova V. 2005. PMID 15598446.
Komistek RD, Dennis DA, Mahfouz M. 2003. PMID 12771818.
Hill and Komistek report variability that precludes a universal no-medial-motion claim.

Correction: added same-specimen fibula, revised posterior-facet rotation centers, and sampled surface-clearance guard. These are illustrative geometric adaptations.
Study illustrations: Pinskerova V, Vavrik P (2020), chapter14, Figures14.1 and14.4, reproduced unaltered under CC BY4.0. https://doi.org/10.1007/978-3-030-24243-5_14 ; https://creativecommons.org/licenses/by/4.0/