ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

understand and implement in the sense of a “simple computational framework”. We
have demonstrated that a reciprocal configuration diagram, that was generated in terms
of two screw axes surfaces during the stance phase, can be used for geometric
representation of the interaction between gait kinematics and ground reaction force.
Therefore, the shape of the reciprocal condition in the diagram can be regarded as the
“genome” of gait pattern under all load-bearing physiological conditions. As reported in
the results section, there exists a unique one-to-one correspondence between the GRF
and the IAK, whose unique characteristic may have a strong clinical implication
regarding gait disorders on a patient-specific basis.
We may state this result (the discrepancies in Figure 4) in a somewhat different
manner. The wrenches about GRF and muscle (act passively as a braking mechanism in
Figure 3) constitute a wrench which is reciprocal to the IAK. However, we also perceive
a portion of wrench by muscle contraction which acts upon a knee to produce the IAK.
The given wrench can in general be resolved into two wrenches: one may in general be
replaced by a wrench on a screw belonging to the screw system, i.e. IAK, which defines
the freedom of the knee, the latter may be termed the reduced wrench (i.e. appropriate
intensity) [9]; The remainder must compound into a wrench in the reciprocal system and
are neutralized by the reaction of the components, indicated as a gap between two
curves (Figure 4).
One can align the IAK along with the GRF to reduce the payload on the
medial/lateral compartment, thus instead transmitting the reaction (braking) torque to
the structure of the whole body. The reciprocal configuration aligns a GRF with a
reciprocal screw such that the reaction (braking) torques and forces on the joint are
eliminated. Special orthotic or orthopaedic treatments which are rich in reciprocal
configuration may be designed for the post-treatment outcome of gait-related disorders,
and the optimal treatment in this sense requires further investigation. Notice that if the
GRF is not exactly aligned with the reciprocal screw, due to a positioning error for
example, the braking torque on the knee joint axes will not be zero, but will still have a
slight value.
Acknowledgments
We would like to thank Professor B.J. Fregly of the University of Florida for making
the data available. The first author extends thanks to Ms. Maria do Amparo of the FMH
library for her prompt services. The first author also thanks his mother, Ms. Soonhee
Won, for her continuous encouragement for this research. Experimental data was
provided for validation through the Grand Challenge Competition to Predict In Vivo
Knee Loads−a part of the Symbiosis project funded by the National Institutes of Health
via the NIH Roadmap for Medical Research (Grant U54 GM072970).
6. REFERENCES
1. Fregly, B.J., et al., Grand challenge competition to predict in vivo knee loads.
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3. Wang, S.L. and K.J. Waldron, A Study of the Singular Configurations of Serial
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