PhD Fekete - SZIE version - 2.2 - Szent István Egyetem

Literature review
Let us follow the description of Mason et al. [Mason et al., 2008]. Note that l 30 represents the
length of the femur (in their actual calculations they considered it 0.45 m) while l 10 represents
the length of the tibia. The flexion angle is denoted as α. The moment arm is represented as d,
while the body weight vector as BW (Figure 2.38):
d ( α)
= l30 ⋅sin(
α / 2)
(2.4)
M N
( α)
= 0.5⋅
BW ⋅d(
α)
= 0.5⋅
BW ⋅l30 ⋅sin(
α / 2)
(2.5)
The quadriceps tendon force (F q ) can be derived from the net knee moment (M N ) and the
effective moment arm (L eff ) of the quadriceps tendon according to Salem and Powers
[Salem and Powers, 2001]:
Where, L eff can be found in Table 2.2.
M
k
( α)
F
q
( α)
= (2.6)
L ( α)
eff
Several authors have investigated the ratio of the patellofemoral forces under extension and
flexion exercises, and obtained very similar results [Denham and Bishop, 1987, Van Eijden et
al., 1986, Yamaguchi and Zajac, 1989, Hirokawa, 1991, Miller, 1991, Hefzy and Yang, 1993,
Gill and O’Connor, 1996]. These have been gathered and plotted in Figure 2.39 and
Figure 2.40:
Fpt/Fq [-]
1.2
1
0.8
0.6
0.4
0.2
0
Van Eijden et al.
Bishop and Denham
Yamaguchi and Zajac
Gill and O'Connor
Miller et al.
Hirokawa
Flexion angle [˚]
0 20 40 60 80 100 120
Figure 2.39. F pt/F q relationship
– 43 –