Elsevier

Clinical Biomechanics

Volume 25, Issue 7, August 2010, Pages 745-748
Clinical Biomechanics

Brief report
Temporal couplings between rearfoot–shank complex and hip joint during walking

https://doi.org/10.1016/j.clinbiomech.2010.04.012Get rights and content

Abstract

Background

Rearfoot pronation–supination and hip internal–external rotation are commonly assumed to be temporally coupled. Many mechanisms of musculoskeletal injury are proposed based on this assumption. Previous studies suggested that this theoretical coupling does not exist. However, recent experimental studies observed relationships consistent with foot–hip mechanical interdependence.

Methods

Three-dimensional kinematics of the lower extremity of 18 healthy subjects, wearing flat trekking sandals, was measured during the stance phase of normal walking. Rearfoot–shank complex motion in the transverse plane (shank internal–external rotation) and frontal plane (rearfoot eversion–inversion) and hip motion in the transverse plane were analyzed. Cross-correlation coefficients were calculated to investigate temporal similarities between curves of rearfoot–shank and hip motions. Pearson correlations were used to investigate relationships between the timings of the peaks of these motions.

Findings

Cross-correlations revealed a strong mean temporal coupling (mean r = 0.77, range 0.56 to 0.92) between shank internal–external rotation and hip internal–external rotation and a moderate mean temporal coupling (mean r = 0.56, range 0.37 to 0.78) between rearfoot eversion–inversion and hip internal–external rotation. Pearson correlations revealed significant (P  0.031) moderate relationships of timing of peak shank internal rotation (r = 0.45) and timing of peak rearfoot eversion (r = 0.62) with timing of peak hip internal rotation.

Interpretation

The findings suggest a temporal coupling of rearfoot pronation with hip internal rotation and rearfoot supination with hip external rotation during walking stance. The between-subjects variability of curves' temporal similarities and the moderate relationships between timings of motion peaks indicate that coupling strength should be clinically addressed on an individual basis.

Introduction

It has been assumed that, during the stance phase of gait, rearfoot pronation–supination is coupled with lower-limb and hip internal–external rotation (McPoil and Knecht, 1985, Tiberio, 1988). This coupling would make rearfoot pronation to be synchronous with hip internal rotation, and rearfoot supination, with hip external rotation. It would also make the timings of rearfoot and hip motions to be interdependent. For example, prolonged rearfoot pronation and prolonged hip internal rotation would be concomitant (Tiberio, 1988). Many proposed mechanisms of musculoskeletal injuries related to abnormal foot and hip mechanics are based on this theoretical coupling (Botte, 1981, Fonseca et al., 2007, Gross et al., 2007, Tiberio, 1988). Patellofemoral pain, for instance, is associated with delayed peak of rearfoot pronation (Barton et al., 2009). The hypothetic injury mechanism is an excessive lateral patellar displacement due to a concomitant prolonged and excessive hip internal rotation (Tiberio, 1988).

Studies that investigated the relationship between foot–ankle motion and lower-limb or hip transverse plane rotations during gait indicated an absence of foot–hip couplings (Nester, 2000, Reischl et al., 1999). However, these studies used procedures that might be inappropriate to study these relationships. They considered the entire foot as a single rigid segment (to address rearfoot/subtalar motion) and used marker sets not currently recommended for error minimization (Chiari et al., 2005, Manal et al., 2000, Schache et al., 2008). Nester (2000) investigated temporal similarity (covariance) between kinematic time series, using Pearson Correlation Coefficients. However, they did not consider possible time lags between curve pairs. This could be another limitation since possible temporal relationships between joints' displacements may show time delays (Derrick et al., 1994, Li and Caldwell, 1999).

Recent experimental findings suggest mechanical interdependence between rearfoot and hip during gait (Snyder et al., 2009, Souza et al., 2009). Increases in late rearfoot pronation cause increases in hip internal rotation during walking (Souza et al., 2009). Strengthening the hip external rotator muscles decreases the ankle supination moment involved in the deceleration of foot pronation during running (Snyder et al., 2009). Therefore, some level of interdependence and synchrony between rearfoot pronation and hip internal rotation, and between rearfoot supination and hip external rotation may exist.

Since proposed mechanisms of injury are based on this theoretical coupling, it is necessary to test its existence. The study of possible temporal couplings should consider possible time-lagged relationships (Li and Caldwell, 1999). Further, investigating associations between timings of motion peaks could clarify whether prolonged rearfoot pronation is associated with prolonged hip internal rotation (Derrick et al., 1994). Thus, the present study analyzed curves' similarities (considering possibly significant time lags) and peak timings of rearfoot–shank and hip kinematics, during walking stance.

Section snippets

Methods

Eighteen young healthy subjects (11 female, 7 male) with mean age, mass and height of 22.89 years (SD 1.46), 62.32 kg (SD 5.56) and 170 cm (SD 5.0), respectively, participated in the study. Inclusion criteria were: no history of surgery or injuries in the lower-limbs or lumbo-pelvic complex; and a maximum body mass index (BMI) of 25. Low to moderate BMIs were required to minimize the influence of soft tissue motion on the kinematic measurements. The mean BMI was 21.56 (SD 0.36). The participants

Results

There were no significant time lags between rearfoot–shank and hip motions, for any of the subjects (i.e. curves' similarities were not significantly stronger at time lags than at their real times). Therefore, the CCs at k = 0 determined the coupling strengths (real-time couplings). The mean CC between shank internal–external rotation and hip internal–external rotation was r = 0.77 (SD 0.09; range 0.56 to 0.92) and between rearfoot eversion–inversion and hip internal–external rotation was r = 0.56

Discussion

The CC analysis identified a strong mean temporal coupling between shank internal–external rotation and hip internal–external rotation, with r-values varying from moderate to strong. It also identified a moderate mean temporal coupling between rearfoot eversion–inversion and hip internal–external rotation, with r-values between moderate and strong (Pohl et al., 2006, Portney and Watkins, 2000). The positive r-values indicate that shank internal rotation and rearfoot eversion are relatively

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Each of the authors has read and concurs with the content in the final manuscript. The material within has not been and will not be submitted for publication elsewhere. A pilot study was presented in the XXV International Symposium on Biomechanics in Sports, in 2007. The authors disclose that there is not any conflict of interest that could have biased this work.

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