Effects of foot orthoses with medial arch support and lateral wedge on knee adduction moment in patients with medial knee osteoarthritis

Abstract

Background:

There is contradictory evidence regarding whether the addition of medial arch supports to laterally wedged insoles reduces knee adduction moment, improves comfort, and reduces knee pain during the late stance phase of gait.

Objectives:

To verify if such effects occur in participants with medial knee osteoarthritis.

Study design:

Randomized single-blinded study.

Methods:

Gait analysis was performed on 18 patients affected by medial knee osteoarthritis. Pain and comfort scores, frontal plane kinematics and kinetics of ankle, knee, and hip were compared in four conditions: without foot orthosis, with foot orthoses, with medial arch support, and with foot orthoses with medial arch support and lateral wedge insoles with 6° and 10° inclination.

Results:

Lower-extremity gait kinetics were characterized by a significant decrease, greater than 6%, in second peak knee adduction moment in laterally wedged insole conditions compared to the other conditions (p < 0.001; effect size = 0.6). No significant difference in knee adduction moment was observed between laterally wedged insole conditions. In contrast, a significant increase of 7% in knee adduction moment during the loading response was observed in the customized foot orthoses without lateral inclination condition (p < 0.001; effect size = 0.3). No difference was found in comfort or pain ratings between conditions.

Conclusion:

Our study suggests that customized foot orthoses with a medial arch support may only be suitable for the management of medial knee osteoarthritis when a lateral wedge is included.

Clinical relevance

Our data suggest that customized foot orthoses with medial arch support and a lateral wedge reduce knee loading in patients with medial knee osteoarthritis (KOA). We also found evidence that medial arch support may increase knee loading, which could potentially be detrimental in KOA patients.

Keywords

Knee adduction moment gait analysis lower extremity insoles pain comfort

Background

Knee osteoarthritis (KOA) is the most prevalent form of osteoarthritis in the lower limbs; it affects 12.1% of the population aged 60 years and older in the United States.¹ Medial tibiofemoral osteoarthritis development is the most common form of KOA. One of the main causes is greater loading in the medial compartment of the knee (around 70% of total loads) than in the lateral compartment during the stance phase of gait.² Medial KOA increases this loading by altering the tibiofemoral alignment with a greater varus angle.³ Laterally wedged insoles (LWI) constitute one of the treatments used to offload the medial compartment of the knee. LWIs are insoles with a higher lateral side, in which the degree of correction depends on the elevation.⁴ Insoles are considered to be moderately effective at relieving knee pain and decreasing knee loading, but there is a lack of quality evidence on whether this kind of device should be recommended.⁵ LWIs are meant to modify lower limb biomechanics during gait by laterally displacing the center of pressure and thus reducing the knee adduction moment (KAM).^4,6 First KAM peak has long been the main variable analyzed due to its relation with medial contact force at knee and osteoarthritis progression.⁷ A recent study showed a correlation between medial contact force at knee and second KAM peak,⁸ so this peak and KAM angular impulse have also been investigated in recent studies of orthotics.^9–11

Wedged insoles can be uncomfortable for KOA patients⁴ due to their individual foot characteristics and the more pronated position caused by the unsupported medial arch of the foot.¹² Recent studies have tested the effect on KAM during gait of adding an arch support to LWI.^12–16 Some authors found a reduction in the KAM during the stance phase of gait with arch support and a lateral wedge.^14,16 However, in some patients, no effect on the KAM is observed.¹³ Studies performed with healthy subjects showed that adding an arch support to LWI minimized the increase in the subtalar valgus angle due to the lateral wedge while maintaining their efficacy at reducing the KAM during the late stance phase of gait.^14,15 KOA patients experienced a smaller decrease in KAM with LWI without arch support than healthy controls.¹⁷ Further evidence is needed to assess the effect of insoles with arch support and with lateral wedge on lower extremity gait kinetics and kinematics in KOA patients.

The aim of this study was to determine the immediate effects of foot orthoses with medial arch support with or without lateral wedge on the frontal plane kinetics and kinematics of the knee joint during walking in a population suffering from KOA. Their influence on frontal plane kinetics and kinematics of the ankle and hip joints, comfort, and knee pain was also evaluated. We hypothesized that foot orthoses with arch support and lateral wedge would reduce KAM during the late stance phase of gait. This reduction would be greater with a higher wedge.

Methods

Participants

This single-blinded study included 18 patients with isolated medial compartment KOA (Table 1). Inclusion criteria were symptomatic medial KOA (Kellgren–Lawrence grade II or III) according to the clinical and radiological criteria of the American College of Rheumatology,¹⁸ knee pain > 31/100 (WOMAC), moderate activity level, varus knee alignment equal or superior to 2°, and a minimum of 2 mm of joint space narrowing on standing radiographs. Knee varus angle was assessed in the frontal plane¹⁹ by measuring the angle between the long axis of the thigh and the shank on standing radiographs.

Table 1.

Participants’ characteristics (n = 18).

Characteristic
Age (years)	54.5 (8.6, 38–74)
Gender, n (%)	8 (44.4) female 10 (55.6) male
Height (m)	1.70 (0.09, 1.58–1.86)
Body mass (kg)	83.5 (9.8, 57.8–98.5)
Body mass index (kg m⁻²)	28.9 (3.8, 22.3–36.0)
Radiographic severity, n (%)^a	15 (83.3) grade II 3 (16.7) grade III
Varus knee alignment (°)	4.5 (2.8)

SD: standard deviation.

Values are reported as means (SD, range) unless otherwise indicated.

Kellgren–Lawrence grade of radiographic disease severity.

Exclusion criteria were rheumatoid arthritis or other inflammatory arthritis, avascular necrosis, a history of periarticular fracture or septic arthritis, bone metabolic disease, pigmented villonodular synovitis, cartilaginous disease, neuropathic arthropathy, synovial osteochondromatosis, total or partial knee arthroplasty, flexion contracture of ipsi- or contralateral knee greater than 15°, hip or ankle joint damage with mobility limitation, obesity (body mass index (BMI) ⩾ 40), intra-articular corticosteroid injection in the affected knee during the two previous months, and reduced mobility (Charnley²⁰).

Patients were recruited through the campus mailing list. Patients diagnosed by their family physician as having KOA were requested to call a research nurse, who screened them for their level of disability and knee pain using the WOMAC score. Then, a radiological assessment, evaluated by an orthopedic surgeon, was necessary to verify inclusion and exclusion criteria. Once the patient agreed to participate in the study, he or she was referred to an orthotist with 10 years’ experience in insole manufacturing to be fitted with custom foot orthoses and then, a week later, went to the gait laboratory for testing (Figure 1). Ethical approval was obtained from the institutional ethics committee, and written informed consent was obtained from all participants.

Figure 1.

Flow of participants through trial.

Apparatus

Kinematic data were acquired by an optoelectronic motion analysis system composed of 13 cameras (FLEX:V100R2; NaturalPoint Inc., Corvallis, OR, USA), capture software (Acquire 3D^™; C-Motion Inc., Germantown, MD, USA), and 42 reflective markers: 26 were attached to anatomical landmarks and four rigid marker clusters made up of four markers apiece were affixed to the thigh and shank of both legs according to the CAST protocol.^21,22 Two force plates (Model BP400600NC; AMTI, Advanced Mechanical Technology Inc., Watertown, MA, USA) were used to acquire kinetic data. Kinematic data were sampled at 100 Hz, while kinetic data were sampled at 1000 Hz. Finally, natural gait velocity and cadence were acquired with a 3.5-m instrumented walkway (GAITRite; CIR System, Sparta, NJ, USA).

A pair of neutral customized foot orthoses (CFOs)—with medial arch supports and without lateral wedge—was made for each participant by the same experienced orthotist (Figure 2). The orthotist measured the height in millimetres of the medial and lateral foot arch in the sitting position using a measuring block. A foot pressure mapping system measured the plantar pressure for a few seconds in the static standing position and the sitting position to detect the high-pressure zones. An in-house software application was then used to determine the three-dimensional (3D) shape of the orthosis based on the arch heights and plantar pressure zones recorded in the sitting position. Participants had to walk for a few minutes while wearing the orthoses and provide feedback on their comfort. The final curves of the orthoses were adjusted if necessary. The mean (±standard deviation (SD), range) height of the medial arch support for all participants was 27.7 mm (±3.3 mm, 17–33 mm). In addition, two pairs of LWI with 6° and 10° inclinations were made for each participant (ethylene vinyl acetate (EVA) with 75–80 durometer density). The orthotist was kept blind to the patient’s grade of KOA and mechanical alignment, and the same material was used for all orthoses.

Figure 2.

Pictures of the different parts composing the foot orthoses: (a) customized foot orthosis made with arch support and without lateral inclination (neutral CFO), (b) 10° laterally wedged insole, and (c) customized foot orthosis made with arch support and with 10° laterally wedged insole (10° CFO). The CFOs were composed of two parts: an ethylene vinyl acetate base with a density of 75–80 durometer and an SPC^® MP (Podiatech, France) cover with a density of 40–45 durometer. The wedges were composed of ethylene vinyl acetate having a density of 75–80 durometer, and the lateral inclinations were built to fit along the entire foot. To optimize participants’ comfort, the custom orthoses fitted each participant and his or her shoes.

Experimental procedure

First of all, participants were instructed to perform six gait trials on the instrumented walkway at a self-selected regular gait speed, starting to walk 3 m before they stepped onto the walkway in order to reach a steady-state walk when their steps were recorded. These trials were processed immediately and determined the natural gait velocity and cadence. Then, each patient walked on an 8m walkway with the force plates located 2.75 and 3.40 m from the start. Participants were instructed to walk following the rate of a metronome, which was adjusted to their self-selected cadence, as measured previously on the instrumented walkway. Before official data gathering began, several trials were carried out to determine the exact distance from the start, so participants’ heel strikes would hit each force plate without modifying their gait pace.

Participants were exposed to four conditions: (1) without orthosis, (2) with CFO with medial arch support and without lateral wedge (neutral CFO; Figure 2), (3) with CFO with medial arch support and 6° LWI (6° CFO; Figure 2), and (4) with CFO with medial arch support and 10° LWI (10° CFO; Figure 2). Participants performed all gait trials wearing their own shoes. Five trials were carried out in each condition and 10 min separated each condition from the following one. The sequence of conditions was randomized to avoid possible cumulative effects of testing conditions on each other. Participants were blinded to the orthoses in their shoes. Randomization depended on the order in which they called the orthotist’s clinic. Before each trial condition, participants were allowed to walk with the insoles on a treadmill for 2 min to ensure accommodation. After each trial condition, knee pain and comfort were assessed with two 20-cm visual analog scales (VAS: 0–100). Higher scores indicate greater pain and greater discomfort on the pain scale and the comfort scale, respectively.

Data analysis

Visual 3D software and modeling (Version 4.93; C-Motion Inc.) were used to process kinematic and kinetic data. Raw markers and force plate data were filtered at 6 Hz with a low-pass Butterworth filter. To evaluate the effectiveness of the foot orthoses with arch supports in the treatment of KOA, primary outcomes were the KAM first and second peaks and KAM angular impulse. Given that the coordination of the legs relies on several joints, a correction to one joint can cause compensation in another joint. For this reason, the joint angles and moments in the frontal plane of the ankle and hip joints were also analyzed. Joint angles were calculated using Cardan angles with an X–Y–Z order of rotation, equivalent to the joint coordinate system.²³ External joint moments were calculated using 3D inverse dynamics and normalized to body weight and height (Bw*Ht). Joint moments were expressed using the proximal segment coordinate system. A custom-written software program (MATLAB 2007b; MathWorks Inc., Natick, MA, USA) was used to find the joint angles and moment peaks and to calculate the other variables listed in Table 2.

Table 2.

Description of biomechanical variables.

Variables	Definitions
First and second peaks KAM	Maximum adduction moment of the knee during the first and the last 50% of the stance phase, respectively
KAM angular impulse	Area under the knee adduction moment–time graph during the stance phase
Ankle eversion moment	Maximum eversion moment during the stance phase (≈15%)
First and second peaks hip adduction moment	Maximum adduction moment of the hip during the first and last 50% of the stance phase, respectively
Vertical GRF	Maximum vertical ground reaction force during the first and last 50% of the stance phase, respectively
Frontal GRF	Frontal ground reaction force at the first and second KAM peaks
Gait velocity	First derivative of the middle of the ASIS-PSIS position on two consecutive strides at mid-distance on the walkway
Step length	Anteroposterior distance between right and left heel markers at heel strike
Step width	Mediolateral distance between right and left heel markers at heel strike
Foot progression angle	Mean angle between the direction of progression and a reference line on the sole of the foot during the stance phase
Knee adduction angle	Maximum knee angle during the stance phase
Hip adduction angle	Maximum hip angle during the stance phase
Knee center of pressure distance (ML knee-COP distance)	Distance between the knee joint center and the center of pressure (COP) at the first and second KAM peaks
Knee lever arm	Perpendicular distance between GRF and knee joint center in laboratory frontal plane at the first and second KAM peaks

GRF: ground reaction force; ASIS-PSIS: anterior superior iliac spine and posterior superior iliac spine; KAM: knee adduction moment; ML: mediolateral.

Gait velocity was measured in m s⁻¹, step length and step width in cm, angle in °, GRF in N, external moment in N m/Bw*Ht, angular moment impulse in N m s/Bw*Ht, and lever arm in mm s.

Statistical analysis

Statistical analysis was done with STATISTICA 8.0 (StatSoft, Inc., Tulsa, OK, USA). Gait data were initially analyzed by repeated measures one-way analyses of variance (ANOVAs) and, when necessary, Tukey’s honest significant difference (HSD) for multiple comparisons was employed as a post hoc test. The non-parametric Friedman test was used to compare the knee pain and comfort VAS score between conditions. Effect sizes (ESs) were reported as partial eta-squared.²⁴ The level of significance was set at p < 0.05.

Results

A 6% and 10% higher KAM was observed in the neutral CFO condition (mean ± SD, 0.352 ± 0.084 N m/Bw*Ht) than in the no orthosis and 6° CFO conditions, respectively, at the first peak (0.330 ± 0.086 N m/Bw*Ht; 0.317 ± 0.078 N m/Bw*Ht; p < 0.001; ES = 0.26; Figure 3). No difference was noted in the first peak between the neutral CFO and 10° CFO conditions (p = .09; 0.332 ± 0.085 N·m/Bw*Ht, 317 ± 0.088 N·m/Bw*Ht). A 8.8% and 10.9% reduction in the second KAM was found in the 6° CFO and 10° CFO conditions, respectively, compared to the other conditions (p < 0.001; ES = 0.58; Figure 3; Table 3). Thus, values decreased from 0.285 ± 0.093 and 0.284 ± 0.092 N m/Bw*Ht in the no orthosis and neutral CFO conditions to 0.260 ± 0.084 and 0.254 ± 0.087 N m/Bw*Ht in the 6° CFO and 10° CFO conditions, respectively (Figure 3; Table 3). A significant decrease in the KAM impulse during the stance phase was seen in the two conditions with lateral wedge compared to gait without orthosis or with a neutral CFO (Table 3; ES = 0.43). No significant difference in the KAM was observed between the 6° CFO and 10° CFO conditions (p > 0.05).

Figure 3.

External knee adduction moment during the stance phase of gait in the four conditions: no orthosis, customized neutral foot orthoses without lateral inclination (neutral CFO), customized foot orthoses with 6° laterally wedged insoles (6° CFO), and customized foot orthoses with 10° laterally wedged insoles (10° CFO).

Table 3.

Summary of values for variables showing means (SD).

Variables	No orthoses	Customized foot orthoses with arch supports			p
	No orthoses	Neutral CFO	With 6° CFO	With 10° CFO
Ratings (%)
Knee pain	23.0 (22.8)	21.8 (18.8)	20.4 (21.2)	24.2 (22.6)	0.90
Comfort of shoes	30.5 (27.8)	31.3 (20.2)	35.3 (20.2)	35.9 (26.4)	0.59
Kinetics
First KAM peak (N m/Bw*Ht)	0.330 (0.086)	0.352 (0.084)^a	0.317 (0.078)^b	0.332 (0.088)	<0.01
Second KAM peak (N m/Bw*Ht)	0.285 (0.093)	0.284 (0.092)	0.260 (0.084)^a,b	0.254 (0.087)^a,b	<0.001
KAM impulse (N m s/Bw*Ht)	12.3 (4.1)	12.9 (3.8)	11.6 (3.5)^a,b	11.6 (3.6)^a,b	<0.001
Peak ankle eversion moment (N m/Bw*Ht)	0.061 (0.027)	0.063 (0.028)	0.077 (0.025)^a,b	0.090 (0.029)^a,b,c	<0.001
First peak hip adduction moment (N m/Bw*Ht)	0.518 (0.093)	0.536 (0.096)	0.518 (0.080)	0.534 (0.102)	0.08
Second peak hip adduction (N m/Bw*Ht)	0.508 (0.084)	0.501 (0.098)	0.495 (0.092)	0.490 (0.099)	0.14
Vertical force at first peak (N)	927 (149)	937 (164)	937 (142)	956 (169)^a	0.03
Vertical force at second peak (N)	903 (110)	880 (108)^a	882 (112)^a	881 (111)^a	<0.001
Spatiotemporal
Gait velocity (m s⁻¹)	1.40 (0.24)	1.41 (0.25)	1.43 (0.26)	1.43 (0.25)	0.07
Step length (cm)	74.5 (8.5)	73.7 (8.4)	74.2 (8.5)	74.1 (8.5)	0.53
Step width (cm)	10.5 (2.6)	10.2 (2.7)	10.6 (2.5)	10.9 (2.7)	0.05
Kinematics
Foot progression angle (°)	13.8 (3.9)	13.9 (3.8)	15.3 (4.0)^a,b	15.9 (4.2)^a,b	<0.001
Maximum knee adduction angle (°)	4.6 (3.6)	4.5 (3.76)	4.4 (3.7)	5.0 (4.2)	0.54
Maximum hip adduction angle (°)	4.9 (3.3)	5.0 (3.7)	5.2 (3.5)	5.2 (3.6)	0.70
ML knee-COP distance at first peak (mm)	29.6 (20.9)	32.5 (20.7)	26.9 (19.7)^b	26.0 (19.1)^a,b	<0.001
ML knee-COP distance at second peak (mm)	30.0 (17.9)	32.0 (17.4)	25.7 (16.1)^a,b	22.9 (14.8)^a,b	<0.001
Knee lever arm at first peak (mm)	35.6 (19.9)	37.8 (19.5)	32.7 (19.2)^b	31.6 (19.1)^a,b	<0.001
Knee lever arm at second peak (mm)	32.8 (23.1)	34.3 (21.4)	31.3 (21.5)^b	28.9 (20.8)^a,b	<0.001

CFO: customized foot orthosis; Bw: body weight; Ht: height; KAM: knee adduction moment; ML: mediolateral; SD: standard deviation; COP: center of pressure.

Different from no orthosis condition.

Different from neutral CFO condition.

Different from 6° CFO condition.

Gait velocity (ES = 0.13) and step length (ES = 0.04) were similar in all four conditions, while step width was greater in the 10° CFO than the neutral CFO condition (p = 0.05; ES = 0.14; Table 3). Foot progression angle was greater in the 6° CFO and 10° CFO conditions than in the other conditions (ps < 0.001; ES = 0.46; Table 3). An increase in the first vertical ground reaction forces at first peak was observed in the 10° CFO condition compared to the no orthosis condition (p = 0.03; ES = 0.16; Table 3), while at the second peak, all three CFO conditions had a significantly lower value than the no orthosis condition (ps < 0.001; ES = 0.30; Table 3). First and second peaks of the mediolateral distance between the center of pressure and the knee joint center and knee lever arm were lower in the 10° CFO condition than in the no orthosis and neutral CFO conditions (ps < 0.01; ES = 0.43 and ES = 0.60, respectively; Table 3). In these variables, the 6° LWI condition had lower values than the neutral CFO at the first and second peak conditions and a lower mediolateral distance between the center of pressure and the knee joint center than in the no orthosis condition at the second peak (p < 0.05).

Similar knee and hip frontal plane kinematics were observed across all experimental conditions (Table 3). The 10° CFO condition led to a greater ankle eversion moment than the other three conditions (ps < 0.001; ES = 0.72; Table 3); in the 6° condition, it was greater than in the no orthosis and neutral CFO conditions. Knee pain and shoe comfort were the same in all four conditions (Table 3).

Discussion

LWIs may decrease stress on the medial tibiofemoral joint (5%–10% reduced KAM);^4,6,25 however, a lack of fit with the individual foot characteristics may lead to discomfort.⁴ Foot orthoses with arch supports are often prescribed by clinicians to optimize patients’ comfort. To the authors’ knowledge, very few studies have examined the differential effects of these CFO on gait,^12,13,15,26 and only one provided evidence that such orthoses can lead to a reduction in KAM among KOA patients.¹⁶ Nakajima et al.¹⁵ and Jones et al.¹⁰ showed that in healthy participants, foot orthoses with medial arch supports permitted a significant reduction in the second KAM peak (8.8% reduction), that is, during the late stance phase of gait, when compared to LWI or no orthosis. Jones et al.¹⁴ observed a significant reduction in the first KAM peak, while Yeh et al.¹⁶ found a decrease in both KAM peaks in KOA patients given foot orthoses with medial arch support. Like Nakajima et al.¹⁵ and Abdallah and Radwan,¹² we found no effect on the first KAM peak of the stance phase of gait. We did observe a decrease in knee lever arm at the first KAM peak in the 10° CFO condition, but this was offset by an increase in the vertical ground reaction forces.

Our study demonstrated that the use of foot orthoses with medial arch support in KOA patients yielded a reduction of more than 6% in the second KAM peak, and this reduction was even greater when the magnitude of the wedge was increased. Kakihana et al.⁶ suggested that reduction in the knee joint varus moment in healthy controls and KOA patients could be explained by the reduction in the knee-ground reaction force lever arm induced by a 6° lateral wedge. Our results confirmed that both the distances between the center of foot pressure and the knee joint center and the knee lever arm were reduced in KOA patients with CFO with a 10° inclination only. The absence of an effect on the knee lever arm with the 6° CFO is contrary to the results of other studies that reported a significant reduction in the lever arm with a 5° or lower LWI without arch support.^9,25 This could be explained by the fact that medial arch support tends to displace the center of pressure medially, as is seen in the neutral CFO condition. So the medial arch support and the lateral wedge had opposite effects on the center of pressure and canceled each other out with the 6° inclination. Thus, we recommend that optimal foot orthoses with medial arch support treatment should provide the appropriate arch support height and amount of lateral wedging. Further research should investigate the best combination of these two parameters to achieve effective treatment without altered comfort.

Furthermore, reduction in the second KAM peak is associated with a more toe-out gait, which induces a lateral shift of the center of pressure location during the late stance phase and reduces the knee-ground reaction force lever arm.^15,27 Reduction in the second KAM peak with lateral wedge inclination is also explained by a reduction in the vertical ground reaction force, directly proportional to the KAM, because the forward progression of the weight shift over the forefoot and the downward acceleration of the center of mass are limited.²⁸ The customization and stiffness of foot orthoses could also help reduce this second peak of the vertical ground reaction force.

The effects of neutral CFO have been reported in only two studies.^13,26 Franz et al.²⁶ observed a 6% increase in KAM in the late stance phase of gait in healthy subjects, while Hinman et al.¹³ noticed no KAM peak difference in KOA patients. Unlike the latter study, our results showed up to an 8% increase in KAM in the early stance in a KOA population. There are two possible explanations of this difference between our studies. First, the characteristics of the foot orthosis material and design of the two studies might have been different. Second, the differences observed might be due to the participants’ response and variability, as Hinman et al.¹³ observed great inter-individual variability in responses to the medial arch support. The increase in medial knee loading with arch support is induced by the elevation of the medial part of the foot, leading to a medial displacement of the center of pressure away from the center of rotation of the knee.²⁹ Thus, the use of foot orthoses with medial arch support and without lateral inclination should not be recommended to the KOA population.

Several studies have reported that LWIs have effects on the ankle,^15,17,30 but very few have assessed their effects on the hip.^25,30 Those studies that did so reported an increase in ankle eversion angle³⁰ and moment with foot orthoses and no significant change in hip adduction moment.^25,30 The same effects were observed in this study. Arch support seems to minimize the valgus effects of LWI on the ankle.

There are some limitations on this study. First, participants wore their own shoes, which may have influenced the results. However, our study design compared participants within repeated conditions, so the statistical results should remain unchanged. Second, unlike previous studies,^31,32 we did not observe any difference in pain scores among all study conditions, notably those with lateral wedges. This may be due in part to the design of the study. The participants wore each foot orthosis and lateral wedge for a relatively short time (lasting five gait trials), and this might be insufficient to induce immediate pain relief. In future studies, the effects on pain and sensations of comfort should be observed over a longer period. In addition, patients who suffer from KOA usually use various painkillers in different daily dosages. Patients were asked to act as they normally do on a day-to-day basis. Hence, painkiller use during this experiment was not controlled. Third, although KAM is correlated with the medial tibiofemoral compartment forces,⁷ a decrease in KAM values does not guarantee a reduction in medial contact forces.⁸ Finally, the experimental protocol meant that foot markers were attached to the footwear, so we did not measure variations in foot movements within the shoes.

Conclusion

In conclusion, the results of this trial have provided further information on the usefulness of LWIs with arch supports in the management of medial KOA. Further research is necessary to confirm this result with short- to medium-term use and as the disease progresses.

Footnotes

Acknowledgements

The authors thank Annie-Pier Fortin for her assistance with the data collection. We gratefully acknowledge the editing work and suggestions by Zofia Laubitz. Yoann Dessery was supported by a scholarship from FRQNT (Fonds de Recherche du Québec – Nature et Technologies), NSERC (Natural Sciences and Engineering Research Council of Canada) and Ergoresearch Inc.

Author contribution

All authors contributed equally in the preparation of this manuscript.

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

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