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

Loading the fully extended knee with 200N causes the medial and lateral menisci to
translate 1.5mm and 2.2mm respectively in the posterior direction relative to the
unloaded fully extended knee. Loading the knee when flexed to 25 degrees with 200N
causes the medial and lateral menisci to translate 1.3mm and 0.6mm respectively in the
posterior direction relative to the unloaded knee in 25 degrees flexion.
Externally rotating the foot when the knee is loaded with 200N and flexed to 25 degrees
causes the medial meniscus to translate anteriorly 6.3 mm and the lateral translates
0.9mm anteriorly relative to the loaded knee flexed to 25 degrees and the foot straight.
This is 0.2 mm anterior to the unloaded neutral position for the medial meniscus and
2.8mm posterior of the unloaded neutral position for the lateral meniscus. Internally
rotating the foot under the same conditions causes the medial meniscus to translate
anteriorly 4.5 mm and the lateral meniscus translates 3.3mm posteriorly relative to the
loaded knee flexed to 25 degrees and the foot straight. This is 1.5 mm posterior to the
unloaded neutral position for the medial meniscus and 7.0mm posterior of the unloaded
neutral position for the lateral meniscus.
5. DISCUSSION AND CONCLUSION
The vast majority of literature investigating meniscal translations is derived from
studies of cadaveric knees where tissue properties, muscle contributions and anatomical
structure are likely to be disrupted. MRI is an established technique for studying
anatomy and disorders of the menisci and the imaging and post-processing methodology
presented in this study have allowed for visualization and quantification of the 3D
movements of the menisci which occur in-vivo during joint loading, during knee flexion
and during transverse plane knee rotations.
Contrary to majority of published findings, the results of our study indicate that the
medial and lateral menisci are equally mobile, translating posteriorly a maximum of
10.6mm and 9.2mm respectively. It is possible that this discrepancy is due individual
variation since [7] also observed equal mobility of both menisci in 20% of subjects
tested. The difference between our results and those of the literature may also be due to
the methods used to describe meniscal motion. The high resolution imaging and 3D
modeling methods of our study allow for clear visualization of meniscus motion in
addition to quantification of meniscus centroid co-ordinate points. It can be seen from
Fig.1 that the lateral meniscus rotates around the anterior horn while the medial
meniscus rotates around the posterior horn in the transverse plane during knee flexion.
These rotational movements are consistent with the anterior and posterior horn motions
previously reported [4, 7] and appears to be a mechanism working in conjunction with
the ACL to resist posterior motion of the femur relative to the tibia during knee flexion.
By introducing rotation of the menisci in the transverse plane it would also appear likely
that there is increased menisco-femoral contact area on the posterior femoral condyles,
thereby reducing the likelihood of posterior horn tears. This observation will be
examined in future Finite Element Analysis studies. The transverse plane rotation of the
menisci which accompany posterior meniscal motion during knee flexion has not been
reported previously in studies employing 2D sagittal MR slice analysis since the motion
is not exclusively in the sagittal plane. Furthermore, the posterior motion of the menisci
are misrepresented by 2D methods since the portion of meniscus visible in a single 2D
MR slice in not consistent as knee flexion changes. Despite the error in selecting the