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

Table 3: Medial and lateral peak pressures in an intact and meniscectomised knees.
Peak lateral Peak medial
pressure (MPa) pressure (MPa)
Healthy Knee 0.88 1.29
Partial Medial Meniscectomy (50%) 0.96 1.53
Total Medial Meniscectomy 0.90 1.83
Total Meniscectomy 1.82 1.79
5. DISCUSSION
In this paper, a verified FE model of the human knee joint was developed. The main
objective was to understand how locations and percentage removal of partial
meniscectomies influence loading in the tibio-femoral compartment of the knee joint.
The stress distributions in a healthy knee was compared to those of a totally
meniscectomised knee, at 20 degrees flexion in the sagittal plane to simulate the weight
acceptance portion of the gait cycle.
It was found that the peak compressive stress over the tibial cartilage increased
approximately two fold for the meniscectomised knee. These results are consistent with
those published by Pena and co-workers (2005) who reported that the peak compressive
stress in the tibial cartilage rose from 2.55 MPa to 4.55 MPa after total meniscectomy.
However, they simulated a load of 1150 N and full extension of the knee. In Pena’s
study, bones were treated as rigid bodies and the cartilage and meniscus material as
linear static. Both studies show that total meniscectomies have undesirable effects as
deduced from this analysis.
Several limitations of our analysis are acknowledged. As a first step, the results were
obtained for a knee joint in the 20 degrees flexed position. Our next step is to
investigate loading in the knee joint at different joint angles. In this study, the meniscus
and cartilage were considered to be single-phase linear and isotropic materials. In future
studies, viscoelastic material properties will be used to better represent the meniscus and
cartilage. Bones were modelled as a linear elastic and isotropic material in this
preliminary study. In fact, although bones have heterogeneous properties [12], our
sensitivity analyses show that a change in material property from 500 MPa to 5000 MPa
contributed to only 6% change in peak pressure at the tibio-femoral joint [3]. In future
studies, we will model ligaments as transversely isotropic hyperelastic materials [9].
6. CONCLUSION
Stress analyses show that peak compressive stress in a meniscectomised knee was
twice that of the intact knee. This study demonstrates the importance of the meniscus
in reducing knee joint contact stress, which is a first step towards understanding the
safe location and proportion of partial meniscectomy.