# Knee pivot motion during passive flexion is highly correlated with pivot motion during level walking - A preliminary study

Rémi Courteille, Jeanne Hélary, Laurence Chèze, Nicola Hagemeister

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Rémi Courteille, Jeanne Hélary, Laurence Chèze, Nicola Hagemeister. Knee pivot motion during passive flexion is highly correlated with pivot motion during level walking - A preliminary study. Multidisciplinary Biomechanics Journal, 2025, 50th congress of the.., 10.46298/mbj.16164. hal-05191716v2

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# Knee pivot motion during passive flexion is highly correlated with pivot motion during level walking
## A preliminary study

Rémi Courteille<sup>a*</sup>, Jeanne Hélary<sup>a</sup>, Laurence Chèze<sup>b</sup>, Nicola Hagemeister<sup>a</sup>

a LIO, École de Technologie Supérieure, Montréal, Canada

b Univ Eiffel, Univ Lyon 1, LBMC UMR_T9406, F-69622 Lyon, France

* Corresponding author: remi.courteille.1@ens.etsmtl.ca

Received date: 04/04/2025

Accepted date: 27/06/2025

Publication date: 27/10/2025

**Keywords:** knee pivot motion, gait analysis, passive flexion

© 2025 The Authors

Licence CC-BY 4.0

Published by Société de Biomécanique

## 1. Introduction

Knee arthroplasty is a common surgery, but still up to 10-20% of patients remain unsatisfied (DeFrance & Scuderi, 2022). This may be because the implant and soft tissue balancing need to be adjusted to match the patients' native kinematics. In this context, the pivot motion is an important key factor, but to our knowledge, it has been measured only per-operatively (Deckard et al., 2022), using computer assisted surgery, without comparing with active movements. Grassi et al. (2020) concluded that there is no significative range of motion difference between active and passive flexion movements, but they did not assess knee pivot motion. Therefore, it remains unclear if the pivot motion that is measured during a passive flexion/extension movement in per-op will be the same during daily activities such as walking. The present work aims at comparing knee pivot motion during a passive flexion movement with the pivot motion calculated during level walking. This is a preliminary study, that is the first step of a project which will lead to give feedback during surgery to drive post-operative pivot pattern. The hypothesis is that pivot motion calculated during passive flexion reflects the one calculated during walking.

## 2. Methods

### 2.1 Data acquisition

Ten (10) young asymptomatic subjects (mean 28.4 ± 4.1 years) were recruited for this study. None of them had any pain or difficulty to walk. Every subject underwent

a knee kinesiography exam using the KneeKG system (Emovi Inc, Montréal, CA). Acquisition began with functional calibration (Hagemeister et al., 2005). Then, the subjects performed two 45-seconds walking trials on a treadmill at comfortable speed (mean 1 ± 0.2 m/s). The trial with the less variability between cycle was selected for analysis. They then laid on a physiotherapy table, still wearing KneeKG femoral and tibial components, and had the instruction to be as passive as possible. One operator took subject's ankle and proceeded to several (3-5) passive flexion-extension movements, from maximal extension to approximately 70° flexion at slow speed. A 15-second acquisition started once the operator felt the knee passive. Median cycle was used for analysis. All data acquisition was performed by the same operator.

### 2.2 Data processing

Gait cycle was divided in two phases, stance and swing. In this study, stance phase extended from 1% (heel strike) to 30% of the gait cycle. Swing phase extended from 61% to 100% of the gait cycle. Sections between 30% and 60% were excluded because of the low rotational speed in this part of gait cycle. Passive flexion motion was divided in cycles based on flexion angle, and then subdivided in ascending and descending flexion phases.

### 2.3 Knee pivot motion calculation

The knee pivot motion was computed as the projected epicondyles amplitude of anteroposterior displacement.
First step of the calculation was to project epicondyles in the tibial transverse plane (Fig.1.A). Amplitude of the anteroposterior displacement relative to the tibia was then calculated for each epicondyle. Ratio of the projected epicondyles anteroposterior displacement amplitude was calculated: Ratio = $d_{medial} / d_{lateral}$. This ratio represents the most translating epicondyle, inducing description of knee pivot motion (Fig.1.B).

<figure><img src="image_3.png" /><figcaption>**Figure 1.** (A) Projection of femoral epicondyles in tibial transverse plane. (B) Knee pivot point calculation based on projected epicondyles amplitude of anteroposterior displacement during a movement. Superior view of tibial transverse plane, posterior at the top.</figcaption></figure>

## 2.4 Comparison passive-level walking

Ratio of the displacement amplitude of the projected epicondyles was calculated for each subject during stance and swing phases and while passive flexion. In every phase, we studied the common range of flexion between passive motion and walking phase. Subjects were excluded if ranges of flexion didn't overlap. We calculated Pearson correlation coefficient between ratios of epicondyles amplitude of displacements during walking and passive flexion.

# 3. Results and discussion

## 3.1 Comparison of knee pivot motion

One subject was excluded of the stance phase analysis because no flexion angle was in common in passive flexion and walking phase. Correlation coefficients during stance and swing phases are shown in Table 1. Both these coefficients are superior to 0.70 (p < 0.01). This means that ratios of projected epicondyles anteroposterior displacement during walking and passive

flexion are highly correlated when considering the gait phases separately.

Full cycle analysis shows also a significative correlation, but $R^2$ is slightly lower, indicating a weaker correlation.

<table><caption>**Table 1.** Correlation coefficient between ratios of epicondyles amplitude of displacements during walking and passive flexion</caption><thead><tr><td>Phase</td><td>R<sup>2</sup></td><td>p-value</td></tr></thead><tbody><tr><td>Stance phase<br/>1% to 30% GC</td><td>0.71</td><td>0.0044</td></tr><tr><td>Swing phase<br/>61% to 100% GC</td><td>0.70</td><td>0.0025</td></tr><tr><td>Full cycle<br/>1% to 100% GC</td><td>0.55</td><td>0.0142</td></tr></tbody></table>

This result means that knee pivot motion is similar during passive movement and walking, when considering stance and swing phase separately. This result is in line with the results from (Gasparutto et al., 2023), who showed that there are some similarities between per-operative passive flexion and walking, in terms of three-dimensional knee kinematics. Our study supports future works, studying links between per-operative and post-operative knee pivot motion.

# 4. Conclusions

This preliminary study confirms that passive pivot motion is highly correlated with the active one. This opens future work to compare intra-operative with post-operative measurements. It will allow exploring indications given by pivot motion during surgery.

## Acknowledgements

This study has been approved by research ethical committee at École de Technologie Supérieure (H20221108) and Centre Hospitalier de l'Université de Montréal (CE22.245). Every participant has signed fully informed consent.

## Conflict of Interest Statement

No conflict of interest.

## Contributor Roles

RC: Conceptualization, Data curation, Investigation, Methodology, Software, Writing original draft;
JH: investigation, Methodology, Software, Writing- review & editing; LC: Project administration, Supervision, Validation, Writing- review & editing; NH: Funding acquisition, Project administration, Supervision, Validation, Writing- review & editing;

## Funding

This study has been funded by the Chaire de recherche Marcelle Gauvreau (École de technologie supérieure).

## Data, software, code availability

No data or code is available.

## References

Deckard, E. R., Ziemba-Davis, M., & Meneghini, R. M. (2022). Tibiofemoral contact forces influence intraoperative kinematic pivot pattern dependent on posterior cruciate ligament resection in primary total knee arthroplasty. *JAAOS Global Research & Reviews, 6*(4), e22.00033. https://doi.org/10.5435/JAAOSGlobal-D-22-00033

DeFrance, M., & Scuderi, G. (2022). Are 20% of patients actually dissatisfied following total knee arthroplasty? A systematic review of the literature. *The Journal of Arthroplasty*, S0883540322009317. https://doi.org/10.1016/j.arth.2022.10.011

Gasparutto, X., Bonnefoy-Mazure, A., Attias, M., Dumas, R., Armand, S., & Miozzari, H. (2023). Comparison between passive knee kinematics during surgery and active knee kinematics during walking : A preliminary study. *PLOS ONE*, 18(3), e0282517. https://doi.org/10.1371/journal.pone.0282517

Grassi, A., Pizza, N., Lopomo, N. F., Marcacci, M., Capozzi, M., Marcheggiani Muccioli, G. M., Colle, F., & Zaffagnini, S. (2020). No differences in knee kinematics between active and passive flexion-ex-tension movement: An intra-operative kinematic analysis performed during total knee arthroplasty. *Journal of Experimental Orthopaedics*, 7(1), 12. https://doi.org/10.1186/s40634-020-00229-7

Hagemeister, N., Parent, G., Van de Putte, M., St-Onge, N., Duval, N., & de Guise, J. (2005). A reproducible method for studying three-dimensional knee kinematics. *Journal of Biomechanics*, 38(9), 1926-1931. https://doi.org/10.1016/j.jbiomech.2005.05.013