Original paper
Effect of foot orthoses on magnitude and timing of rearfoot and tibial motions, ground reaction force and knee moment during running

https://doi.org/10.1016/j.jsams.2008.05.001Get rights and content

Abstract

Changes in magnitude and timing of rearfoot eversion and tibial internal rotation by foot orthoses and their contributions to vertical ground reaction force and knee joint moments are not well understood. The objectives of this study were to test if orthoses modify the magnitude and time to peak rearfoot eversion, tibial internal rotation, active ground reaction force and knee adduction moment and determine if rearfoot eversion, tibial internal rotation magnitudes are correlated to peak active ground reaction force and knee adduction moment during the first 60% stance phase of running. Eleven healthy men ran at 170 steps per minute in shod and with foot orthoses conditions. Video and force-plate data were collected simultaneously to calculate foot joint angular displacement, ground reaction forces and knee adduction moments. Results showed that wearing semi-rigid foot orthoses significantly reduced rearfoot eversion 40% (4.1°; p = 0.001) and peak active ground reaction force 6% (0.96 N/kg; p = 0.008). No significant time differences occurred among the peak rearfoot eversion, tibial internal rotation and peak active ground reaction force in both conditions. A positive and significant correlation was observed between peak knee adduction moment and the magnitude of rearfoot eversion during shod (r = 0.59; p = 0.04) and shod/orthoses running (r = 0.65; p = 0.02). In conclusion, foot orthoses could reduce rearfoot eversion so that this can be associated with a reduction of knee adduction moment during the first 60% stance phase of running. Finding implies that modifying rearfoot and tibial motions during running could not be related to a reduction of the ground reaction force.

Introduction

Excessive rearfoot eversion (REV) and tibial internal rotation (TIR) during repetitive motions such as running have been associated with Achilles tendinopathy, medial tibial stress syndrome, patellofemoral pain syndrome and knee injuries.1, 2 Foot orthoses are prescribed to align the rearfoot and tibia as well as limiting rearfoot eversion and tibial internal rotation during locomotion. Previous studies reported that foot orthoses reduced either REV3 or TIR.2, 4 Because the timing and magnitude of REV and TIR attenuate ground reaction force and dissipate stress, their reduction may not be the only function of foot orthoses.5, 6, 7 Limiting foot and tibial rotations by means of foot orthoses could also reduce muscle force and modify lever arms.8 These changes in the components of joint moment could affect load distribution at the knees. Generally, the effect of changes in timing and magnitude of REV and TIR with the use of foot orthoses on ground reaction forces and muscle moments is not well understood during running.

Timing of peak REV, TIR and knee flexion must be synchronised during early stance phase of gait for cushioning external force and absorbing shock.7 If REV and TIR peak continue beyond mid-stance during knee extension, this speculated to an antagonist motion and knee injury.7 Subotnick9 reported that peak REV and TIR must occur before mid-stance to attenuate the peak vertical reaction force and the foot must supinate to become rigid at push-off. Little evidence exists on the timing among the peak REV, TIR and vertical ground reaction force during the stance phase of running. To our knowledge, no research has addressed the contributions of these timing events to peak vertical ground reaction forces.

Vertical ground reaction forces have been proposed as indications of loading conditions.10, 11 They could increase when normal foot and tibial motions are restricted or exaggerated.11 Perry and Lafortune11 reported that the active vertical ground reaction force (AVGRF) increased with the use of medially posted orthoses when the peak REV angle was reduced by 6.7° during running. In contrast, no significant changes in peak AVGRF was observed when REV decreased by 3°12 or when the rearfoot was everted excessively.11 These findings suggest that the magnitude of lower-limb motion could contribute to the vertical ground reaction force during running. Though foot orthoses control rearfoot eversion and tibial rotation (without regard to knee flexion), their contribution at reducing the peak vertical ground reaction force is still unclear.

Knee adduction moment (KAM) is thought to increase load in the medial aspect of the tibial plateau and femoral condyle, thereby causing knee pain in runners.13 To our knowledge no investigation was carried out to determine if changes in the REV and TIR magnitudes caused by foot orthoses could be associated to peak KAM during running. Because REV and TIR as well as peak AVGRF and KAM occur during the first 60% stance phase of running, we hypothesized that foot orthoses perturb their relationships during this period of stance phase. This study aimed to test if foot orthoses modify the magnitude and time to peak of REV, TIR, peak AVGRF and KAM and determine if REV and TIR magnitudes are correlated to peak AVGRF and KAM during the first 60% stance phase of running.

Section snippets

Method

Eleven able-bodied men having an average age of 27.9 (S.D. 4.5) years, weight of 86.1 (S.D. 7.0) kg and height of 179.0 (S.D. 5.9) cm volunteered for this research. The number of participants was based on a α of 0.05 and a β of 0.20 according to Erdfelder et al.14 None of the participants had any orthopedic or neurological ailments affecting their running gait. The experimentation procedures were approved by the Hospital Ethics Committee and were explained to all participants.

Six cameras (Motion

Results

Fig. 2 shows the mean magnitudes of the four dependent variables for the shod and shod/orthoses conditions during running. With semi-rigid orthoses, REV magnitude and peak AVGRF decreased, respectively by an average of 40% (4.1°; p = 0.001) and 6% (0.96 N/kg; p = 0.008), when compared with the shod condition. No statistical difference was found in the mean TIR magnitude (p = 0.06) and peak KAM (p = 0.19).

For the normalised time to peak values, a significant main effect of variables was observed (F3,30 = 

Discussion

The results of the present study suggest that wearing a semi-rigid foot orthosis significantly reduces REV magnitude and active ground reaction force with no significant decrease in TIR magnitude and peak KAM. Results revealed that there was a trend for a reduction in TIR (p = 0.06) by reducing REV during running. These findings are in accordance with MacLean et al.,3 but in contrast to Nawoczenski et al.,4 Nester et al.6 and Stacoff et al.2 Variability in the movement pattern in the lower-limb

Practical implications

  • Clinicians should be aware that controlling the frontal plane motion of foot by the use of orthoses could be associated with a reduction of excessive asymmetrical loading at the knee.

  • Coaches and trainers should consider that the shock absorbing characteristic of orthoses could be more effective in reducing the peak active vertical ground reaction force in activities, such as landing, which have high loading conditions.

Acknowledgments

Partial funding for this project was obtained from the Ministry of Sciences, Research, and Technology of Iran and the Natural Science and Engineering Council of Canada.

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