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Knee joint forces in uphill, downhill and level walking

Authors:
Knee joint forces in uphill, downhill and level walking at different gradients
H. Schwameder, R. Roithner, R. Burgstaller, E. Müller
Institute of Sport Science, University of Salzburg, Austria
Introduction
Lower extremity joint loads in walking change substantially with the gradient as it has been reported in
several studies (Schwameder et al. 2000, Davis et al. 1995, Kuster et al. 1995). The most distinct
differences concerning net joint forces and moments have been found for the knee joint (Kuster et al. 1995,
Schwameder et al. 2000). The actual knee joint forces concerning this particular issue, however, have not
been reported in the literature so far. Thus the purpose of this study is to determine structure forces within
the knee joint in level, uphill and downhill walking as a function of the gradient. The results may contribute
to find the biopositive window of knee joint loading in walking and hiking as a basic preventive concept
and to develop rehabilitation training programs.
Methods
22 healthy students (28 yrs, 1.76 m, 72.5 kg) were asked to walk on a ramp with an integrated force plate
(AMTI, 500 Hz) at different gradients. Both, the ramp and the force plate were adjustable to declinations
and inclinations from –24° to +24° in steps of 6°. 2D kinematic data (sagittal plane, 50 Hz) were collected
using a video camera located perpendicular to the ramp. During data analysis the local coordinate systems
were aligned and the data sets synchronized. A planar knee model was used to calculate knee joint forces
based on the collected kinematic and kinetic data (Schwameder et al. 1999). All knee joint forces calculated
(tibiofemoral compression [Fct] and shear forces [Fst], patellofemoral compression forces [Fcp], patellar
tendon forces [Fp] and quadriceps tendon forces [Fq]) were normalized to body weight (BW) and
time-normalized to support phase from heel-strike to toe-off.
Results
Table 1 shows the averaged peak values of the flexion moments and selected knee joint forces as a function
of the gradient. All knee joint forces, except the tibiofemoral shear forces, were lowest for level walking
and increased continuously with the gradient both, in uphill and downhill walking. Downhill walking
caused higher peak knee joint forces than uphill walking at the same gradient. In downhill walking at 24°
knee joint forces can be up to six times higher compared to level walking. Interesting is the result that the
tibiofemoral shear forces decrease in uphill walking with the inclination of the slope.
Two examples of the time history of knee joint forces (tibiofemoral shear forces and patellofemoral
compression forces) for level as well as for uphill and downhill walking at 24° are presented in Fig. 1.
Gradient
[deg]
Flex. moment
[BW]
Fct
[BW]
Fst
[BW]
Fcp
[BW]
Fp
[BW]
Fq
[BW]
-24 2.47 7.2 1.4 7.1 5.9 7.5
-18 2.17 6.3 1.3 5.9 5.1 6.3
-12 1.95 5.8 1.2 4.4 4.6 5.2
-6 1.28 4.0 0.9 2.3 2.3 3.0
0 0.75 2.7 0.6 1.3 1.7 1.8
6 0.97 3.3 0.7 2.0 2.3 2.5
12 1.25 4.0 0.7 3.2 3.0 3.6
18 1.28 4.3 0.4 4.4 3.2 4.6
24 1.41 4.6 0.3 5.7 3.5 5.7
Table 1: Knee flexion moments and knee joint forces during downhill, level and uphill walking at diffent gradients
Figure 1: Tibiofemural shear forces and patellofemoral compression forces in downhill, level and uphill walking
Both, in level and downhill walking high tibiofemoral shear forces indicating loads on the ACL can be
observed in the first part of stance phase. Compared to level walking the peak forces in downhill walking
are up to three times higher. In uphill walking the shear forces are small during the entire stance phase.
In level walking the patellofemural compression forces show a typical wave with local maxima at 25% and
85% of stance phase. During the entire stance phase the forces are relatively small. In uphill walking the
Fcp-forces increase substantially in the first part of stance phase compared to level walking while in the
second half of stance phase the shape of the curves are more or less the same. The highest patellofemoral
compression forces can be observed for downhill walking. The shape of the curve is similar to the one for
level walking. The amount of the forces, however, are about six times higher during the entire stance phase.
Discussion
The results of this study show that the knee joint forces (peak values and time courses) in walking change
substantially with the inclination of the slope. The knee joint forces differ both, concerning peak values and
time courses, from knee flexion moments and illustrate clearly the necessity of joint models to study loads
on joint structures. Many hikers suffer from knee pain and injuries after long and excessive descents. The
results of this study intensify the assumption that high loadings on knee joint structures cause pain and long
term injuries observed in hikers.
The results contribute to training recommendations in walking and hiking to optimally stimulate knee joint
structures without overloading. Patients after ACL reconstruction, for example, are recommended to
stimulate muscle activity by level and uphill walking. By this most of the structures are highly loaded but
there is only little stress on the ACL as the shear forces are small. On the other hand downhill walking
should be avoided completely due to the high stress on the ACL in this situation.
Retropatellar knee pain is common in hikers during or after long descents. This fact can be explained by the
high patellofemoral compression forces during the entire stance phase. It is worth to think about measures
to reduce these high loadings by adaptation of the downhill walking speed and technique or by using hiking
poles (Schwameder et al. 1999).
References
Davis M et al. 1995. Clin Orthop 310, 211-217.
Kuster M et al. 1995. Clin Biom 10, 79-84.
Schwameder H et al. 1999. J Sports Sciences 17, 969-978.
Schwameder H et al. 2000. Proceedings 18. Intern. Symposium on Biom. in Sports, Hong Kong, 983.
Tibiofemoral shear forces
-0.5
0
0.5
1
1.5
0 25 50 75 100
% stance phase
*BW
-24°
+24°
Patellofemoral compression forces
-2
0
2
4
6
8
0 25 50 75 100
% stance phase
*BW
-24°
+24°
... The patellofemoral compressive forces happen when two body sections are aligned into each other. Those are expected to increase continuously with the slope both in uphill and downhill walking (Schwameder et al., 2001). However, on the same slope, the patellofemoral compressive forces tend to be more aggressive in downhill. ...
... For our group, with a mean of 69.59 of body weight, this represents approximately 210 kg of force experienced at each step during the descent. Schwameder et al. (2001) found patellofemoral compressive forces of 2.3 xBW when downhill at a 10.5% grade. Normally, the high patellofemoral compression forces are dominant in the entire stance phase at downhill. ...
... The more challenging uphill was found in stage 2 of the trail 3 "Lapa dos Dinheiros", showing tibiofemoral shear forces of 0.63 xBW at a 20% climb. Schwameder et al. (2001) found values near 0.7 at slopes near 20% grade. At uphill, the stance phase happens step by step at higher ground promoting a lower relative knee angle and range of motion. ...
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The aim of this study was to characterize knee joint forces in different trails from the Serra da Estrela with distinct characteristics. Twenty-nine subjects (20 males and 9 females), mean of 28.04±10.79 years, 1.73±0.09 m of height and 69.59±11.00 kg of body mass volunteered for this study. In separate days, all subjects underwent three hikes (trail 1: circular, 10970m; trail 2: linear, 9053m; trail 3: circular, 7536m). A GPS device (Fenix 5, Garmin, USA) was used to ensure a consistent 5 km·h-1 pace and tracking the slopes. The knee joint forces, namely the maximum patellofemoral compressive force (MaxPcF), the maximum tibiofemoral shear force (MaxTsF) expressed as times the body weight (xBW) and the load equivalent (LE) were estimated. The MaxPcF was 2.1, 1.8 and 2.1, and the MaxTsF was 0.83, 0.80 and 0.83 for trails 1, 2 and 3, respectively. The MaxPcF for trail 1 is equivalent to a flat 17386 m walk and MaxTsF is equivalent to a 10980 m walk. The MaxPcF for trail 2 is equivalent to a flat 12605 m walk and MaxTsF is equivalent to a 8320 m walk. The MaxPcF for trail 3 is equivalent to a flat 12357 m walk and MaxTsF is equivalent to a 7532 m walk. According to the LE, trail 1 can be classified as “moderate”, and trails number 2 and 3 are classified as “pleasant”. Main data suggests that trail number 2 elicited less knee compression and shear forces. In contrast, trails number 1 and 3 are less appropriate for those who suffered from previous knee pain.
... hip, knee and ankle, using appropriate rigid body models or finite element models (Nisell, 1985;Kuster et al, 1994;van den Bogert et al, 1999;Giddings et al, 2000;Anderson and Pandy, 2001;Bergmann et al., 2001;Heller et al, 2001;Schwameder et al., 2001;Stansfield et ah, 2003;Taylor et al., 2004). ...
... Graded walking and ascending or descending stairs are associated with an increase of lower extremity joint loading compared with level walking. Compared with level walking, uphill and downhill walking or ascending and descending stairs cause changes in the ground reaction force patterns (Grampp et al., 2000), a substantial increase of hip joint loading Heller et al., 2001), an increase of lower extremity joint power and work and an increase of knee joint forces (Reilly and Martens, 1972;Nisell, 1985;Kuster et al, 1994;1995;Schwameder et al, 2001;Taylor et al, 2004). There is empirical evidence that increased joint loading causes pain and injuries in the lower extremity joints (Blake and Ferguson, 1993;Kuster et al, 1994;Schwameder, 2004). ...
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Lower extremity joint loading during walking is strongly affected by the steepness of the slope and might cause pain and injuries in lower extremity joint structures. One feasible measure to reduce joint loading is the reduction of walking speed. Positive effects have been shown for level walking, but not for graded walking or hiking conditions. The aim of the study was to quantify the effect of walking speed (separated into the two components, step length and cadence) on the joint power of the hip, knee and ankle and to determine the knee joint forces in uphill and downhill walking. Ten participants walked up and down a ramp with step lengths of 0.46, 0.575 and 0.69 m and cadences of 80, 100 and 120 steps per minute. The ramp was equipped with a force platform and the locomotion was filmed with a 60 Hz video camera. Loading of the lower extremity joints was determined using inverse dynamics. A two-dimensional knee model was used to calculate forces in the knee structures during the stance phase. Walking speed affected lower extremity joint loading substantially and significantly. Change of step length caused much greater loading changes for all joints compared with change of cadence; the effects were more distinct in downhill than in uphill walking. The results indicate that lower extremity joint loading can be effectively controlled by varying step length and cadence during graded uphill and downhill walking. Hikers can avoid or reduce pain and injuries by reducing walking speed, particularly in downhill walking.
  • H Schwameder
Schwameder H et al. 1999. J Sports Sciences 17, 969-978.
  • M Davis
Davis M et al. 1995. Clin Orthop 310, 211-217.
  • M Kuster
Kuster M et al. 1995. Clin Biom 10, 79-84.