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

4. RESULTS
The methods used to measure the PD gave different results (Table 1).
Table 1: PD (mm) for Healthy and PFPS subjects at different knee positions
Knee Angle Healthy PD1 PD2 PD3 PD4 PD5
Position Subject
30° 1 6.08 1.95 1.10 0.97 2.20
2 6.97 1.98 1.54 1.95 2.80
3 6.50 1.90 1.16 1.81 2.40
45° 1 6.88 2.20 1.10 1.41 2.60
2 7.50 2.10 1.24 2.43 3.00
3 7.32 1.98 1.10 2.58 2.50
Knee Angle
Position
PFPS PD1 PD2 PD3 PD4 PD5
30° 1 7.13 3.18 1.33 2.27 2.95
2 6.93 3.00 1.52 1.46 2.90
3 5.30 2.00 0.67 1.04 1.90
45° 1 7.59 3.36 1.36 2.75 3.10
2 8.25 3.38 1.39 2.50 2.92
3 7.68 2.20 1.36 3.10 2.90
Fig. 2. PD (mm) in lateral (L) and medial (M) side of the PF joint for healthy and PFPS
subjects at 30° and 45° knee position using method PD2
In healthy subjects, PD1, PD2, PD4, and PD5 show that PD increases with knee flexion
angles. PD3 has an opposite trend. PD is greater for PFPS subjects at 30° and 45° using
PD1 and PD2. Overall the PD for PFPS subjects is higher compared to the healthy
subjects. Higher PD occurred in medial side of PFPS joint at 30° flexion and at 45° a
slight increase of PD is obtained and similar PD is measured in medial and lateral sides.
Figure 2 shows the variation in PD at medial and lateral side of the PF joint for healthy
and PFPS subjects.
Generally, the contact stress and von Mises stress in cartilage increased with the
increase in flexion angle in healthy and PFPS joint and the largest values were obtained
in the PFPS joint (Fig. 3 and Fig. 4).
(a) (b)
Fig. 3. Contact pressure in lateral (L) and medial (M) side of the PF joint at 30° and 45° flexion
for healthy and PFPS joints at: (a) femur cartilage surface and (b) patellar cartilage surface