knee joint moments and patellofemoral pain syndrome in runners part i

Figure 1: Stance phase knee joint moments in the sagittal, frontal and transverse planes comparing asymptomatic
(n=20) to PFPS (n=20) runners, running heel-toe, with a shoe, at 4.0 m/s.(CASE CONTROL Study Design)
Figure 2: Stance phase knee joint moments in the sagittal, frontal and transverse planes comparing asymptomatic
(n=12) to PFPS (n=6) runners, running heel-toe, with a shoe, at 4.0 m/s.(PROSPECTIVE Study Design)
Knee Moment [Nm]
study condition group n
max extension (SD) p-value max abduction (SD) p-value max ext rotation (SD) p-value
asymp 20 124.1 (47.5) -103.1 (35.6) 27.9 (16.2)
case control shoe
0.69 0.16 0.14
pfps 20 129.1 (29.6) -127.3 (66.1) 35.8 (16.5)
asymp 12 132.1 (31.2) -49.9 (33.6) 12.9 (10.2)
shoe
0.05
0.16
0.12
pfps 6 101.7 (18.8) -74.7 (29.2) 21.5 (10.5)
prospective
asymp 12 128.9 (33.0) -45.5 (31.2) 11.8 (7.8)
barefoot
0.03 *
0.08
0.03 *
pfps 6 94.6 (16.1) -75.2 (27.0) 22.4 (10.2)
Table 1: Comparison of average maximal knee moments and standard deviations in the sagittal, frontal and transverse
planes for both study designs. Only shoe running was collected for the Case Control Study.
condition variable [unit] sub 1 sub 2 sub 3 sub 4 sub 5 sub 6
∆ (max extension moment) % -25.5 -23.8 -3.9 -18.5 -19.1 -47.5
shoe ∆ (max abduction moment) % 139.9 21.2 72.7 -48.1 73.8 38.6
∆ (max external rot moment) % 176.2 -14.0 96.9 -57.5 81.4 119.2
∆ (max extension moment) % -35.6 -27.5 -2.6 -32.0 -35.9 -25.8
barefoot ∆ (max abduction moment) % 165.1 81.5 89.4 -21.3 54.3 22.4
∆ (max external rot moment) % 239.7 74.5 129.2 -13.7 74.2 34.1
Table 2: Individual subject values for the Prospective Study. Values shown are differences in % from the average of the
asymptomatic group. A positive value indicates a higher moment compared to the asymptomatic average.
DISCUSSION
Increased knee joint loading in the frontal (ab-adduction moments) and transverse
(external-internal rotation moments) planes may lead to increased stresses within or around
the patellofemoral joint and thus leading to pain. Both maximal abduction and maximal
external rotation knee moments were approximately 20% higher for the injured runners in
the case control study. No statistical differences were seen. Results of the prospective
study showed a similar trend. These differences became statistically significant for the
external rotation moment when looking at barefoot running. More importantly, the PFPS
group had a 65% higher maximal knee abduction moment and a 90% higher maximal
external knee rotation moment. For the prospective study, individual differences revealed
that 5 of the 6 injured subjects had a 30% or greater value for the abduction and external
rotation moment for barefoot running. This pattern was also evident for 8 of the 20 injured
subjects in the Case Control study. There is a strong possibility that increased knee joint
moments are contributing factors leading to the onset of PFPS in runners.
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