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

contact area is very different for the three cases, which seems to be more concentrated
on the lower anterior site for the sliding contact cases, whereas it is more spread on
the whole anterior surface for the fully attached case. The meniscal total
displacements differ significantly for each case, being reduced to those elements in
the femoro-meniscal contact for the fully attached case, a slight increase on the
number of elements that present displacement for the horns section attachment case,
and a displacement of almost the entire menisci for the tips attachment case, being the
lateral meniscus the one that experiences the largest displacement, especially in its
anterior site. The femoral total displacement also significantly differs for each case
scenario, gradually increasing with the degree of menico-tibial sliding contact, and a
much larger knee flexion can be observed for the tips attachment case.
4. Discussion and Conclusion
The three case scenarios represented show the high influence that meniscal
attachment had on the performance of the knee. The case in which just a few nodes at
the tips were attached, presented meniscal displacement similar to those from
cadaveric and in vivo studies [12-14]. The increase of effective stress on the areas
around the attachments in the FE model would not occur in reality as they seem to be
attached to the tibia through several ligaments [16-18]. The same may be applied to
the shear strain. Therefore, a model with the menisci attached through ligaments
should be tested to check on the same effects and see the degree of error obtained.
Another important result was the effect on femoral displacement and rotations, since
menisco-tibial displacement allowed for a higher degree of motion of the femur in a
controlled manner, i.e., before the collapse of the model. This provides evidence on
the role of menisci as stabilisers. The horns sections attachment case allowed for both
larger femoral motion and much longer simulation time compared to the fully
attached case. This case demonstrates increased stability and motion. In the nodal tips
attachment case the length of simulation time was lower than for the horns sections
case, since it allowed for a much longer femoral rotation, leading to a much faster
collapse of the model. Perhaps the most interesting finding was the effect on the
maximum value of the ACL first principal stress and its distribution. With the
increase of the menisco-tibial sliding motion, this maximum value significantly
decreased, and the stress was more uniformly distributed through the length and width
of the ACL. This is evidence of how the increase of freedom of motion of the menisci
helps to accommodate the knee in a position that minimises the stress suffered by the
ACL and avoids its concentration in a reduced area, what could lead to ligament
damage. The femoral cartilage shear stress on the patello-femoral contact did not
show a correlation with the degree of menisco-tibial sliding contact, only that it was
higher than for the fully attached case. This is explained since the increase of motion
of the femur would equally create an increase of the patello-femoral motion and
interaction, which is less controlled than for the fully attached case. This could be
compensated with the addition of the patellar cartilage, which would absorb part of
the stress suffered by the femoral cartilage in this model.
In conclusion, the increase in the menisco-tibial sliding contact allowed for a higher
degree of motion of the femur, a lower and more uniform stress distribution on the
ACL, and a larger motion of the menisci.