Original research
Immediate effect of valgus bracing on knee joint moments in meniscectomised patients: An exploratory study

https://doi.org/10.1016/j.jsams.2016.03.005Get rights and content

Abstract

Objectives

Patients undergoing medial arthroscopic partial meniscectomy are at increased risk of developing and/or progressing knee osteoarthritis, with increased medial compartment load being a potential contributor. The aim of this study was to evaluate the immediate effect of a valgus unloader knee brace on knee joint moments in patients following medial arthroscopic partial meniscectomy.

Design

Within-participant design.

Methods

Twenty-two patients (age 35–55 years) who had undergone medial arthroscopic partial meniscectomy within the previous 8–15 months completed three-dimensional analysis of gait, forward lunge and one-leg rise during two conditions: with and without a valgus unloader knee brace. Outcome measures included the peak and impulse of the knee adduction moment and the peak knee flexion moment.

Results

The peak knee flexion moment increased during brace condition for forward lunge (mean difference [95% CI]) 0.54 [0.27–0.82] (Nm/(BW × HT)%), p < 0.001 and one-leg rise (mean difference 0.45 [95% CI 0.08–0.82] (Nm/(BW × HT)%), p = 0.022). No other significant differences were found between conditions in any of the included tasks.

Conclusions

A significant effect of the knee brace was detected in terms of an increase in peak knee flexion moment during the more demanding tasks such as forward lunge and one-leg rise. This increase implies enhanced stability of the knee provided by the brace, which may induce increased knee function and knee-related confidence during strenuous tasks. Future research is required to explore the structural implications.

Introduction

Osteoarthritis (OA) in the tibiofemoral and patellofemoral compartment is common in patients following arthroscopic partial meniscectomy (APM).1 Despite strong evidence questioning the efficacy of APM to manage symptomatic meniscal tears,2 a large volume of these procedures are performed.3 Thus, investigation into treatments aiming to prevent or delay the development or progression of early OA in this patient population is warranted.

The external knee adduction moment (KAM) is an indicator of mediolateral knee joint load distribution where the peak KAM has been positively associated with structural joint change in patients following medial APM.4 Studies from patients with established knee OA also report an association between higher KAM and structural degeneration during gait.5, 6 The KAM is predominantly determined by the product of the ground reaction force (GRF) vector and the perpendicular distance of this force to the centre of the joint (i.e. the frontal plane lever arm).7 Increased varus malalignment is thought to increase the frontal plane lever arm and consequently increase the KAM.7 Varus malalignment has been shown to progress over time in patients following medial APM8 and partially account for the increase in KAM during gait.9 Thus, varus malalignment is a potential target for treatments to address in patients following medial APM.

Valgus unloader knee braces are a non-surgical treatment strategy for patients with medial compartment knee OA.10 Theoretically, the brace applies an external valgus moment, which plausibly reduces load in the medial tibiofemoral compartment10 and retard structural disease progression.11 According to a recent systematic review, valgus knee bracing can reduce the KAM during walking, with moderate-to-large effects in patients with established medial knee OA.10 A similar effect of valgus bracing could potentially exist in patients following medial APM, although to our knowledge this has not yet been investigated.

In addition to the KAM, the external knee flexion moment (KFM) is of interest. Patients following medial APM reportedly have a higher peak KFM12, 13 that appears to increase over time.13 These results are of potential significance as there is an association between higher peak KFM during gait and patellar cartilage volume loss over 2 years in this population.4 Although the mechanisms by which a valgus unloader knee brace would alter the KFM are unclear, it is important to evaluate the immediate effects of bracing on the KFM.

Given the association between knee joint moments during gait and structural change, reducing knee joint moments during gait is considered desirable. In addition to gait, we considered more physically demanding tasks appropriate to middle-aged APM patients. The purpose of this study was to test the hypothesis that wearing a valgus unloader knee brace would reduce the peak KAM during gait in middle-aged individuals following APM at high risk of developing or progressing early knee OA. The secondary exploratory aims of this study was to assess the immediate effect of the valgus unloader brace on KAM impulse and the peak KFM during gait, and all three moment parameters (peak KAM, KAM impulse and peak KFM) during a forward lunge and one-leg rise.

Section snippets

Methods

Participants aged 35–55 years who had undergone an isolated medial APM were recruited from the existing cohort study “Knee Arthroscopy Cohort Southern Denmark” (KACS).14 Exclusion criteria were: major cartilage damage defined as deep visible clefts or bone observed at arthroscopy; co-morbidities affecting lower extremity function; current self-reported back problems; very low activity level (i.e. gait function restricted to indoor walking only); unable to read or understand Danish. Assessment

Results

Twenty-two patients who had undergone a medial APM within the previous 8–15 months participated in this study. Descriptive characteristics are presented in Table 1. Participants were middle-aged, predominantly female, overweight, and had neutral static alignment (Table 1). The majority of meniscal injuries resulted from a non-traumatic incident (Table 1).

The KOOS scores indicate on average mild pain during activity, mild other symptoms and functional restriction during daily life. Sport and

Discussion

The aim of this exploratory study was to examine the immediate effect of a valgus unloader knee brace on joint moments during three functional tasks, in a group of middle-aged patients 12 months following medial APM. While no evidence was found to suggest an immediate effect of the valgus unloader knee brace on peak KAM or KAM impulse for any of the tasks assessed, the immediate effect of wearing the brace demonstrated an increase in peak KFM during a forward lunge (10%) and one-leg rise (8%)

Conclusion

Our preliminary findings suggest that the immediate effect of valgus bracing in people following a medial APM increases the peak KFM during challenging tasks including forward lunge and one-leg rise. Alterations in the peak KFM provide the impetus for conducting larger scale studies investigating the implication on physical function and structural change.

Practical implications

  • Valgus bracing does not appear to alter measures of knee joint loading during gait, although individual results vary.

  • Valgus bracing could be beneficial to meniscectomised patients by providing greater knee-related confidence during demanding activities.

  • The results may aid development of conservative management of meniscectomised patients.

Acknowledgements

We thank Össur, Reykjavik, Iceland who provided us with the braces and consulting assistance. Össur was not involved in study design, writing or editing this manuscript. MH was supported by a PhD scholarship from a National Health Medical Research Council, Australia program grant (#631717) and an International Travel Grant from the International Society of Biomechanics. Finally, the authors would like to express gratitude to the patients who voluntarily participated in the present study.

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