Knee Joint Models for Kneeling Biomechanics - Computational Biomechanics of the Musculoskeletal System - page 89

S, Mises
(Avg: 75%)

+2.120e+01
+8.000e+00
+7.333e+00
+6.667e+00
+6.000e+00
+5.333e+00
+4.667e+00
+4.000e+00
+3.333e+00
+2.667e+00
+2.000e+00
+1.333e+00
+6.667e-00
+0.000e+00

Medial

Lateral

FIgure 7.5

(See color insert.) The von Mises stress of menisci under a 1000 N compressive load.

cartilage damage, according to Grodzinsky et al. (2000), then we can estimate the safe criterion for
kneeling. According to our results (Figure 7.5), 600-N compressive loads (causing 4.805-MPa peak
contact pressure) for each knee have the potential to cause knee disorders. In other words, single
stance kneeling or double stance kneeling with loads greater than one times body weight could be
dangerous to the knee joint. Therefore, when in a kneeling position, the loads on the knee should
be kept below 600 N. According to the results, contact area alone is not adequate for determining
the risk of injury.

7.3.2 S treSS d iStriBution of m eniSci and B oneS
Besides the cartilage, the stress distribution of menisci and bones was also calculated from
this model. The von Mises stress of the lateral meniscus is approximately equal to that of the
medial one, which indicates that there should be an equivalent risk of menisci injury for both
sides (Figure 7.5). The maximum von Mises stress of bones is 26.15 MPa, located at the contact
point between the patella and the ground (Figure 7.6). This suggests an injury risk for patella
disorders.
The FE model of a kneeling position provided a detailed stress distribution of the knee joint.
However, there are still several limitations. First, the material properties used in our model are
based on previous literature that does not correspond to a specific subject. Therefore, the exact
value should be used cautiously. Second, here we only simulated a case of 90 degrees of flexion.
It would be important to investigate the influence of the flexion angle and make comparisons
between crouching and kneeling. In addition, we only used a static model to investigate the con-
sequence of constant loading. The result of impacts also needs to be considered using a dynamic
model with more sophisticated consecutive equations.
In spite of these limitations, the von Mises stress, contact pressure, and contact area were deter-
mined for a kneeling position. The region of high risk for injury was identified and a comparison
made with other studies of the standing position. All of these findings help us better understand the
mechanical influence of kneeling and provide information that could be used to prevent associated
injuries.