Effect of a_knee_ankle_foot_orthosis_on_knee

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Effect of a Knee-Ankle-Foot Orthosis on Knee Kinematics
and Kinetics in an Individual with Varus Knee Alignment
Huda H. Alfatafta, BSc (Hons), MSc, Stephen Hutchins, PhD, Anmin Liu, PhD, Richard Jones, PhD
ABSTRACT
Background: Knee valgus braces are used to reduce knee load and varus deformities in individuals with medial compartment
osteoarthritis (OA). The purpose of this study was to determine whether the kinematics and kinetics of the knee are improved
when wearing a knee-ankle-foot orthosis (KAFO) compared with knee valgus braces while walking and stair climbing.
Materials and Methods: One male individual (with 10° of knee varus) was assessed with a control shoe, custom, and off-the-shelf
(OTS) Unloader knee valgus braces, and a custom-made KAFO in situ during walking and stair climbing.
Results: The KAFO significantly reduced the knee varus angle compared with the shoe and both knee valgus braces during
walking and stair climbing, as well as the first peak of the external knee adduction moment (EKAM) during walking and the
knee adduction angular impulse (KAAI) during ascending compared with the shoe. No significant differences were noted
between the custom and OTS knee valgus braces in any measures.
Conclusions: Knee-ankle-foot orthoses may be recommended for individuals with high knee varus angles. (J Prosthet Orthot.
2016;28:186–190.)
KEY INDEXING TERMS: knee varus, knee motion, EKAM, knee valgus brace, KAFO
BACKGROUND
Knee osteoarthritis (OA) has been shown to occur in 10% of
individuals aged 55 years and older in the United Kingdom.1
The medial compartment is the most common location.2
Medial
compartment knee OA is mainly associated with clinical
symptoms and radiological changes, along with an increased
knee varus, which consequently also increases the external
knee adduction moment (EKAM) by shifting the knee joint
center more laterally and the center of the load medially, espe-
cially during stance phase. This increases the load on the medial
compartment, which has been associated with pain and progres-
sion of medial knee OA.3,4
Several conservative treatments have
therefore been developed for reducing this excessive knee varus
angulation, resulting increase in the EKAM.
One such treatment is the use of knee valgus braces, which
are available as either custom-made or off-the-shelf (OTS)
devices. Custom-made knee valgus braces have been shown
to be more effective in reducing both the EKAM variables
(first and second peak) and the knee varus angles than OTS
devices,5
with reductions in EKAM between 5.5% and 33%
being demonstrated,6,7
while other investigations have found
no significant reductions in EKAM during walking8–10
or during
stair climbing.10
One additional effect in one study has been a
demonstrable reduction in knee flexion during swing phase.11
An alternative orthosis that could be useful in reducing the
knee varus angle and the EKAM as well as potential compressive
forces is a custom-made knee-ankle-foot orthosis (KAFO), which
would take advantage of longer lever arms inherent in the design
of the device. A cosmetic KAFO that is composed of a medial
single upright with a single axis knee joint has the potential
to keep the tibia and foot in a corrected position via an ankle-
foot orthosis (AFO) section. This would encourage a reduction
in knee varus deformity, prevent hyperextension, and poten-
tially improve knee flexion by shifting the body's load anterior
to the hip and posterior to the knee joint.12
However, to the
authors' knowledge, no previous studies have investigated
the effect of a KAFO on correcting a varus-aligned knee. The
purpose of this study was therefore to examine the effect of
a cosmetic KAFO on knee kinematics and kinetics in the sag-
ittal and frontal planes and to compare these data with both a
custom and OTS knee valgus brace and also without wearing
an orthosis during walking and stair climbing activities.
CASE DESCRIPTION AND METHODS
PARTICIPANT CHARACTERISTICS
One male individual with a 10° knee varus deformity (age,
45 years; mass, 85 kg; height, 1.68 m) participated in this study.
Inclusion criteria were presence of a knee varus angle of more
than 7° measured manually by a goniometer, no previous knee
injury, no pain during ambulation, and being able to use stairs
without any external assistance. Ethical approval was obtained
HUDA H. ALFATAFTA, BSc (Hons), MSc, is affiliated with the Faculty
of Rehabilitation Sciences, Department of Prosthetics and Orthotics,
University of Jordan, Amman, Jordan.
STEPHEN HUTCHINS, PhD; ANMIN LIU, PhD; and RICHARD JONES,
PhD are affiliated with the School of Health Sciences, University of Salford,
Brian Blatchford Building, Manchester, UK.
Disclosure: The authors declare no conflict of interest.
Copyright © 2016 American Academy of Orthotists and Prosthetists
Correspondence to: Huda Alfatafta, BSc (Hons), MSc, Faculty of Reha-
bilitation Sciences, Department of Prosthetics and Orthotics, Univer-
sity of Jordan, Queen Rania St, Office number 521, Amman, 11942,
Jordan; email: H.h.al-fatafta@edu.salford.ac.uk
CASE REPORT
186 Volume 28 • Number 4 • 2016
Copyright © 2016 by the American Academy of Orthotists and Prosthetists. Unauthorized reproduction of this article is prohibited.

2. from the local institution, and informed consent was provided
before the enrollment.
DATA COLLECTION
The participant attended two sessions. In the first session, a
cast was made by a certified orthotist with the affected knee in
its maximal comfortable corrected position to allow fabrication
of the KAFO. The individual was also measured for a custom-
made and OTS knee valgus brace Ossur Unloader One (Össur
UK, Manchester, UK) as per manufacturer's guidelines. The
KAFO was a single upright design with an Ottobock knee joint
(17lk1 = L/R1–5) from Germany, which tolerates up to 100 kg of
loading, with 8 mm thickness and 23.6 mm width, and which
incorporates a 5° knee flexion stop. The KAFO was also designed
with a simple hinged ankle joint to allow free movement and
manufactured in 4.5 mm copolymer polypropylene (Figure 1).
In the second session, the participant undertook a gait assess-
ment in the following test conditions: wearing control shoes
(Ecco-Zen), Ossur UnloaderOne custom, or OTS knee valgus
braces, and a custom KAFO. The participant was asked to per-
form five trials with each condition during walking and stair
climbing (ascending and descending) whereby the speed of the
activity was controlled by a metronome. There was a 10-minute
washout period between conditions. The CAST marker set tech-
nique13
was used whereby rigid clusters of four nonorthogonal
markers were positioned over the lateral shank, lateral thigh, and
sacrum to track the movements of the limbs. Retroreflective
markers were glued securely to the control shoes with the foot
modeled as a rigid segment (on the first, second, and fifth meta-
tarsal heads, and calcaneal tubercle). Further markers were
attached to medial and lateral malleolus, lateral and medial
femoral epicondyle, greater trochanter, anterior superior iliac
spine, posterior superior iliac spine, and iliac crest.
GAIT ANALYSIS
Three-dimensional gait analysis was performed using
16-infrared Qualisys OQUS cameras (Qualisys AB, Gothenburg,
Sweden) at a sample rate of 100 Hz and two embedded AMTI force
plates in a walkway (model-BP600400; AMTI, Advanced Mechan-
ical Technology Incorporation, Watertown, MA, USA), which cap-
tured ground reaction force at a sample frequency of 1000 Hz.
For the stair climbing, an interlaced (AMTI) stairway was used,
which has three steps that are fixed over two force plates.14
DATA ANALYSIS
Postprocessing calculation of the kinematics and kinetic data
was conducted in Visual3D software (version-5; C-Motion Inc,
Rockville, MD, USA). Motion and force plate data were filtered
with a Butterworth fourth-order bidirectional low-pass filter
with cutoff frequencies of 6 Hz and 25 Hz.11
All lower-limb seg-
ments were modeled as rigid bodies with anatomical frames
defined by the landmarks surrounding the joints. Knee joint
kinematics were calculated using an X-Y-Z Euler rotation
sequence equivalent to the joint coordinate system.15
The net
external knee moments were calculated using an inverse
dynamic approach after normalization of the data according
to the participant's mass (Nm/kg).
STATISTICS
SPSS (version 20; IBM SPSS, Chicago, IL, USA) was used to
perform a repeated measure analysis of variance (ANOVA) with
a post hoc Bonferroni correction (corrected P = 0.05). Key out-
come variables assessed included maximum sagittal plane knee
angle at initial contact (IC) and mid swing, maximum frontal
plane knee angle during stance phase, maximum frontal plane
knee moment in early and late stance, the maximum and mini-
mum sagittal plane knee moment, and knee adduction angular
impulse (KAAI) values.3
Because the small sample size, all trials
were assessed instead of the mean of all trials.
RESULTS
WALKING SPEED
As expected, no significant changes in walking speed (m/s)
were found among the test conditions. The average speed was
Figure 1. The KAFO design.
Journal of Prosthetics and Orthotics Effect of a KAFO on Knee Kinematics and Kinetics
Volume 28 • Number 4 • 2016 187
Copyright © 2016 by the American Academy of Orthotists and Prosthetists. Unauthorized reproduction of this article is prohibited.

3. 0.97 ± 0.04, 0.4 ± 0.0, and 0.45 ± 0.0 m/s during walking, stair
ascent, and descent, respectively, for all conditions.
KNEE KINETICS DURING WALKING AND
STAIR CLIMBING
During walking, the KAFO significantly reduced the first peak
value of EKAM compared with the shoe by 11.4% (P = 0.04). No
significant difference was found compared with either the OTS
or custom-made knee valgus braces, although reductions of
15% and 12.6%, respectively, were seen. The KAFO also reduced
the second peak of the EKAM during walking by 12%, 12.3%,
and 9.5% compared with the shoe, the custom, and the OTS
knee valgus brace, respectively, but this was only significant
compared with the custom valgus brace (P = 0.00).
During stair climbing, no significant changes were seen in
the first or second EKAM peak during stair climbing between
the conditions (Table 1, Figure 2). With regards to the sagittal
plane, no significant changes were seen in knee kinetics when
comparing the KAFO to any of the other test conditions during
either test condition.
KNEE ADDUCTION ANGULAR IMPULSE
The KAAI was reduced when using the KAFO compared with
the shoe during walking and stair ascent and descent, but this
Table 1. Mean and standard deviation and P Value of the knee adduction moment and knee flexion and extension moment among
different conditions
Variables
Mean ± SD P
Shoe OTS Custom KAFO
Shoe vs.
OTS
Shoe vs.
custom
Shoe vs.
KAFO
KAFO vs.
custom
KAFO vs.
OTS
Custom vs.
OTS
EKAM first peak Wa 0.70 ± 0.01 0.71 ± 0.01 0.73 ± 0.02 0.62 ± 0.0 1.0 1.0 0.04 0.07 0.07 1.0
As 0.85 ± 0.3 0.79 ± 0.4 0.78 ± 0.02 0.79 ± 0.05 1.0 1.0 1.0 1.0 1.0 1.0
De 0.81 ± 0.1 0.90 ± 0.2 0.97 ± 0.6 0.81 ± 0.4 0.17 0.38 1.0 0.86 0.46 1.0
EKAM second
peak
Wa 0.65 ± 0.01 0.63 ± 0.02 0.65 ± 0.01 0.57 ± 0.01 1.0 1.0 0.09 0.00 0.07 1.0
As 0.46 ± 0.01 0.48 ± 0.02 0.45 ± 0.02 0.41 ± 0.02 1.0 1.0 0.78 0.05 0.17 1.0
De 0.75 ± 0.02 0.75 ± 0.01 0.77 ± 0.02 0.74 ± 0.01 1.0 1.0 1.0 1.0 1.00 1.0
KAAI Wa 0.38 ± 0.02 0.37 ± 0.02 0.35 ± 0.01 0.31 ± 0.0 1.00 1.00 0.22 0.41 0.07 1.00
As 0.42 ± 0.0 0.42 ± 0.0 0.41 ± 0.0 0.31 ± 0.1 1.00 1.00 0.00 0.05 0.03 1.00
De 0.43 ± 0.01 0.44 ± 0.02 0.48 ± 0.01 0.41 ± 0.01 1.00 0.12 1.0 0.06 1.0 1.00
Knee flexion
moment
Wa 0.48 ± 0.04 0.55 ± 0.03 0.58 ± 0.02 0.70 ± 0.04 1.00 0.27 0.33 0.60 0.42 1.00
As 0.80 ± 0.5 0.82 ± 0.2 0.78 ± 0.03 0.82 ± 0.03 1.00 1.00 1.00 1.00 1.00 1.00
De 1.00 ± 0.03 0.98 ± 0.02 0.98 ± 0.02 1.03 ± 0.03 1.00 1.00 1.00 1.00 1.00 1.00
Knee extension
moment
Wa 0.28 ± 0.02 0.27 ± 0.02 0.28 ± 0.0 0.24 ± 0.01 1.00 1.00 1.00 1.00 1.00 1.00
As 1.2 ± 0.5 0.8 ± 0.9 1.1 ± 0.05 1.5 ± 0.1 0.56 1.00 1.00 0.28 0.09 0.09
De 0.51 ± 0.2 0.62 ± 0.2 0.64 ± 0.01 0.11 ± 0.05 1.00 1.00 0.37 0.30 0.46 1.00
Bold result shows significant result run with ANOVA with a post hoc Bonferroni correction.
OTS, off-the-shelf; KAFO, knee-ankle-foot orthosis; EKAM, external knee adduction moment; KAAI, knee adduction angular impulse; Wa, walking; As, ascending;
De, descending.
Figure 2. EKAM during walking (A), stair ascent (B), and stair descent (C) during the different test conditions.
Alfatafta et al. Journal of Prosthetics and Orthotics
188 Volume 28 • Number 4 • 2016
Copyright © 2016 by the American Academy of Orthotists and Prosthetists. Unauthorized reproduction of this article is prohibited.

4. only reached significance during ascent (P = 0.00; Table 1). In
addition, a significant difference was noted between the KAFO
and OTS for this parameter (P = 0.03) during stair ascent. No
significant differences in KAAI were found between the knee
valgus braces for any task.
KNEE KINEMATICS DURING WALKING AND
STAIRS CLIMBING
The knee adduction angle was significantly decreased when
using the KAFO by 8.2° and 6° during walking and stair descent
(P = 0.0 and 0.03, respectively) and insignificantly by 12° during
stair ascent compared with the shoe. In addition, the KAFO sig-
nificantly reduced the knee varus angle by 3°, 15°, and 6.8° com-
pared with the custom knee valgus brace (P = 0.0 for all) and by
2.7°, 12.4°, and 3.5° compared with OTS knee valgus brace dur-
ing walking, stair ascent, and descent, respectively (P = 0.04,
0.0, and 0.01, respectively; Table 2). The custom and OTS knee
valgus braces significantly reduced the knee varus angle during
walking compared with the shoe (P = 0.0 both), with the OTS
significantly reducing the knee varus during descent (P = 0.03).
In the sagittal plane, the KAFO increased the knee flexion
angle at IC significantly compared with the shoe and OTS dur-
ing walking (mean difference, 8.6° and 4.1°, respectively). How-
ever, all the test conditions insignificantly reduced knee flexion
at mid swing during walking (between 2° and 7°) compared
with the shoe. Both of the knee valgus braces produced a sig-
nificant increase in knee flexion at IC during walking com-
pared with the shoe, with the OTS also increasing knee flexion
at IC during stair descent.
DISCUSSION
This case study investigated the ability of a custom KAFO to
reduce EKAM/KAAI and knee varus during walking and stair
climbing to provide a potential new treatment option for indi-
viduals with a knee varus deformity and OA. The KAFO was
more effective than both of the knee valgus braces in decreasing
the knee varus during walking and stair climbing with
decreases of up to 12°. The efficiency of a KAFO in reducing
a knee varus angle is mainly related to the offset joint, which
was used to correct knee deformity in the frontal plane (knee
valgus/varus), with the length of the KAFO applying more force
over a more extensive tissue area than knee valgus braces.
This meant that it would theoretically be able to correct the
deformity more effectively. Furthermore, the KAFO has a more
intimate and extensive fit on the lower limb than that provided
by an OTS device.
The KAFO reduced the first peak of EKAM by a greater
margin than either of the knee valgus braces (11.4%, 15%,
and 12.6% compared with the shoe, OTS, and custom knee
valgus braces, respectively) during walking. No significant
changes were seen during stair climbing, and this could be
due to a high knee varus angle that was seen (up to 30°),
and the interventions cannot reduce it efficiently. The mech-
anism for the difference is due to the KAFO design, which can
apply four points of pressure over the thigh, knee, and shank
to correct tibial alignment and keep the foot in a relatively
neutral position. This design would shift the ground reaction
force more laterally and the knee joint center more medially,
thereby reducing the EKAM. Although the knee valgus braces
also apply three points of pressure, the longer length of the
KAFO compared with the knee valgus braces helped the KAFO
to apply more force correction than the knee valgus braces
due to longer lever arms.
In the current study, neither knee valgus brace produced any
significant effect on EKAM during walking and stair climbing,
which is similar to that demonstrated in previous studies.8–10
This could be due to the high varus angle of the participant
(<7°) and due to the shorter length of the knee valgus braces,
which could apply less force than KAFO to correct tibia and foot
alignment. All The test conditions did show a reduced knee
flexion at mid swing, but this was only significant for the
OTS brace compared with the shoe during stair ascent. This
could be due to the tight straps around the knee joint11
or ax-
ial rotation of the brace during movements.
Table 2. mean and SD of knee angle in sagittal and frontal planes among conditions
Mean ± SD P
Shoe OTS Custom KAFO
Shoe vs.
OTS
Shoe vs.
custom
Shoe vs.
KAFO
KAFO vs.
custom
KAFO vs.
OTS
Custom vs.
OTS
Knee flexion
at IC
Wa 2.5 ± 0.6 7.0 ± 0.5 7.8 ± 0.6 11.1 ± 0.6 0.03 0.02 0.00 0.28 0.03 1.0
As 66.8 ± 1.1 65.2 ± 0.7 67.2 ± 0.9 67.3 ± 0.6 1.0 1.0 1.0 1.00 0.36 1.0
De 14.7 ± 0.4 19.9 ± 0.4 17.9 ± 0.5 15.6 ± 0.8 0.01 0.10 1.00 0.31 0.01 0.00
Knee flexion at
mid swing
Wa 74.1 ± 0.2 70.5 ± 3.2 72.3 ± 1.3 72.4 ± 0.4 1.0 1.0 0.31 1.0 1.0 1.0
As 107.0 ± 0.8 103.1 ± 0.8 100.3 ± 1.5 101.5 ± 1.7 0.01 0.24 0.05 1.0 1.0 1.0
De 105.9 ± 1.4 104.3 ± 1.2 102.9 ± 1.2 98.2 ± 0.08 1.0 1.0 0.15 0.05 0.22 1.0
Maximum knee
abduction
Wa 17.4 ± 0.4 11.9 ± 0.3 12.2 ± 0.1 9.20 ± 0.2 0.00 0.00 0.00 0.00 0.04 1.0
As 30.3 ± 0.6 30.5 ± 0.3 33.5 ± 0.3 18.3 ± 0.1 1.0 0.08 0.00 0.00 0.00 0.00
De 21.4 ± 0.5 19.9 ± 0.4 22.2 ± 0.4 15.4 ± 0.3 0.03 1.0 0.00 0.00 0.01 0.10
Bold results show significant result according to ANOVA was run with 4 factors (shoe, OTS, custom knee brace, and KAFO) with a post hoc Bonferroni correction.
OTS, off-the-shelf; KAFO, knee-ankle-foot orthosis; IC, initial contact; Wa, walking; As, ascending; De, descending.
Journal of Prosthetics and Orthotics Effect of a KAFO on Knee Kinematics and Kinetics
Volume 28 • Number 4 • 2016 189
Copyright © 2016 by the American Academy of Orthotists and Prosthetists. Unauthorized reproduction of this article is prohibited.

5. There are obvious limitations in this case study. It examined
the effect of the orthoses on one individual and was repeated on
the same day. In addition, the washout time was short be-
tween conditions, which could have affected the results; how-
ever, orthoses generally make mechanical changes in the
joint, and one would expect the effects to reduce back to base-
line values directly after they removed each device.
CONCLUSIONS
In conclusion, using a custom KAFO produced a larger cor-
rection of the knee varus deformity and a reduction in EKAM
by theoretically applying greater force over the thigh and shank.
These results give preliminary indications that a KAFO could be
a useful alternative orthosis for individuals with a high varus
angle and medial knee OA. Further work will be needed to fur-
ther evaluate the clinical and biomechanical benefits of a
KAFO in a larger number of subjects with different severities
of unicompartmental knee OA.
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Alfatafta et al. Journal of Prosthetics and Orthotics
190 Volume 28 • Number 4 • 2016
Copyright © 2016 by the American Academy of Orthotists and Prosthetists. Unauthorized reproduction of this article is prohibited.