We characterize the concept of a “knee axis” and further the concept of “invariant.” It is now generally recognized that one of the features of the tensegrity (prestressable to the same configuration) allows the knee tensegrity system to be in producing the knee instantaneous axis (KIA). We found that the line of the ground reaction force (GRF) vector is very close to the KIA. It aligns the knee joint with the GRF such that the reaction forces are torqueless. The reaction to the GRF will then be carried by the whole structures on the knee tensegrity instead. The use of knee tensegrity model introduces the new useful dimensions of sensitivity in foot loading to the knee axis alignment. We demonstrated a method to determine ideal placement of the tibial tunnel with respect to the KIA. Such placement in vivo has the potential to reliably produce an isokinetic graft without risk of impingement.
Part of the book: Knee Surgery