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. 2014 Jul 8;9(7):e102098.
doi: 10.1371/journal.pone.0102098. eCollection 2014.

Cross-talk correction method for knee kinematics in gait analysis using principal component analysis (PCA): a new proposal

Audrey Baudet  1 , Claire Morisset  2 , Philippe d'Athis  3 , Jean-Francis Maillefert  4 , Jean-Marie Casillas  5 , Paul Ornetti  4 , Davy Laroche  2
Affiliations

Cross-talk correction method for knee kinematics in gait analysis using principal component analysis (PCA): a new proposal

Audrey Baudet et al. PLoS One. .

Abstract

Background: In 3D gait analysis, the knee joint is usually described by the Eulerian way. It consists in breaking down the motion between the articulating bones of the knee into three rotations around three axes: flexion/extension, abduction/adduction and internal/external rotation. However, the definition of these axes is prone to error, such as the "cross-talk" effect, due to difficult positioning of anatomical landmarks. This paper proposes a correction method, principal component analysis (PCA), based on an objective kinematic criterion for standardization, in order to improve knee joint kinematic analysis.

Methods: The method was applied to the 3D gait data of two different groups (twenty healthy subjects and four with knee osteoarthritis). Then, this method was evaluated with respect to three main criteria: (1) the deletion of knee joint angle cross-talk (2) the reduction of variance in the varus/valgus kinematic profile (3) the posture trial varus/valgus deformation matching the X-ray value for patients with knee osteoarthritis. The effect of the correction method was tested statistically on variabilities and cross-talk during gait.

Results: Cross-talk was lower (p<0.05) after correction (the correlation between the flexion-extension and varus-valgus kinematic profiles being annihilated). Additionally, the variance in the kinematic profile for knee varus/valgus and knee flexion/extension was found to be lower and higher (p<0.05), respectively, after correction for both the left and right side. Moreover, after correction, the posture trial varus/valgus angles were much closer to x-ray grading.

Conclusion: The results show that the PCA correction applied to the knee joint eliminates the cross-talk effect, and does not alter the radiological varus/valgus deformation for patients with knee osteoarthritis. These findings suggest that the proposed correction method produces new rotational axes that better fit true knee motion.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Plug-in-Gait marker set.
Figure 2
Figure 2. Mean and standard deviation of knee joint rotations during gait for a single typical subject before (grey dash-dotted line and light-grey area) and after correction (black solid line and grey area).
Dotted vertical line indicates the mean toe off value for this subject.
Figure 3
Figure 3. Averaged ab/adduction angle (mean and SD) during gait for each of the four OA patients before (grey dash-dotted line and light-grey area) and after correction (black solid line and grey area).
Dotted vertical line indicates mean toe off.
See this image and copyright information in PMC

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