ARTHRITIS & RHEUMATISM
Vol. 50, No. 10, October 2004, pp 3129–3136
© 2004, American College of Rheumatology
A Six-Month Followup of a Randomized Trial
Comparing the Efficacy of a Lateral-Wedge Insole
With Subtalar Strapping and an In-Shoe Lateral-Wedge Insole
in Patients With Varus Deformity Osteoarthritis of the Knee
Yoshitaka Toda and Noriko Tsukimura
Objective. To assess the effect of a lateral-wedge
insole with elastic strapping of the subtalar joint on the
femorotibial angle in patients with varus deformity of
Methods. The efficacy of a wedged insole with
subtalar straps and that of a traditional wedged insole
shoe insert were compared. Sixty-six female outpatients
with knee osteoarthritis (OA) were randomized (accord-
ing to birth date) to be treated with either the strapped
or the traditional inserted insole. Standing radiographs
with unilateral insole use were used to analyze the
femorotibial angles for each patient. In both groups, the
baseline and 6-month visual analog scale (VAS) scores
for subjective knee pain and the Lequesne index scores
for knee OA were compared.
Results. The 61 patients who completed the
6-month study were evaluated. At baseline, there was no
significant difference in the femorotibial angle (P ?
0.66) and the VAS score (P ? 0.75) between the 2
groups. At the 6-month assessment, the 29 subjects
wearing the subtalar-strapped insole demonstrated a
significantly decreased femorotibial angle (P < 0.0001)
and significantly improved VAS scores (P ? 0.001) and
Lequesne index scores (P ? 0.033) compared with their
baseline assessments. These significant differences were
not observed in the 32 subjects assigned to the tradi-
tional shoe-inserted wedged insole.
Conclusion. These results suggest that an insole
with a subtalar strap maintained the valgus correction
of the femorotibial angle in patients with varus knee OA
for 6 months, indicating longer-term clinical improve-
ment with the strapped insert compared with the tradi-
Osteoarthritis (OA) of the knee is a leading cause
of chronic disability in adults (1). Few of the factors
contributing to the progression or advancement of knee
OA have been identified, but knee alignment is thought
to play an important role. Varus and valgus malalign-
ment have been shown to increase the risk of subsequent
medial and lateral progression, respectively, of knee OA
(2). In the normally aligned ambulating knee, load is
disproportionately transmitted through the medial com-
partment (3). Varus deformity further increases the total
load passing medially through the joint during walking
(4). Patients with knee OA usually present with major
involvement in only 1 compartment, and the medial
compartment is involved nearly 10 times more fre-
quently than is the lateral compartment (5).
One of the first forms of conservative mechanical
treatment developed for patients with medial compart-
ment knee OA was the laterally wedged in-shoe orthosis.
Keating et al (6) reported that in 61% of patients with
medial knee OA, the pain score improved with use of a
wedged insole. Yasuda and Sasaki (7) speculated that
the beneficial effect of the lateral-wedge insert was
attributable to the reduction in medial knee joint surface
loading, with a concurrent reduction in lateral tensile
forces, even though the device failed to correct the
femorotibial angle in patients with medial compartment
knee OA. It is plausible that, with use of the inserted
insole, movement of the talus may prevent calcaneal
valgus correction, thereby preventing femorotibial val-
Yoshitaka Toda, MD, Noriko Tsukimura, PT: Toda Ortho-
pedic Rheumatology Clinic, Suita, Osaka, Japan.
Dr. Toda has a patent for the insole with subtalar strapping
used in this study.
Address correspondence and reprint requests to Yoshitaka
Toda, MD, Toda Orthopedic Rheumatology Clinic, 14-1 Toyotsu-cho,
Suita, Osaka 564-0051, Japan. E-mail: firstname.lastname@example.org.
Submitted for publication January 6, 2004; accepted in re-
vised form June 30, 2004.
gus correction (Figure 1b). Vaes et al (8) demonstrated
that use of a tape bandage or brace significantly re-
stricted talar tilt. In their study, use of such support
reduced talar tilt from 13.3° to 4.9°.
Studies of conservative alternatives to high tibial
osteotomy for realignment of the femorotibial angle
have revealed that the limitations of inserted insoles can
be minimized through use of an insole with elastic subtalar
strapping (Figure 1c). In a previous study, standing radio-
graphs of the knee and ankle joints in anteroposterior
views were used to analyze the femorotibial, talocalcaneal,
and talar tilt angles in patients randomized to wear either
the strapped insole or the traditional insole (9). In each
patient, the angles with and without an inserted or a
subtalar-strapped insole were compared. In both groups,
the talocalcaneal angle with the insoles was significantly
increased compared with the angle without the insoles.
However, the talar tilt angle with the insole was signifi-
cantly decreased only in the strapped-insole group. In the
inserted-insole group, there was no significant difference in
the talar tilt angle with and without the insole. A significant
difference in the femorotibial angle with insole use was
detected in the strapped-insole group, but the femorotibial
angle was not significantly changed with use of the inserted
The realignment produced by use of the insole
with subtalar strapping led to the conclusion that use of
an insole with elastic fixation leads to valgus angulation
of the talus, resulting in correction of the femorotibial
angle in patients with varus deformity knee OA. Further
studies demonstrated the efficacy of the insole with
subtalar strapping, use of which resulted in pain reduc-
tion (at night, upon awakening, and on standing from a
seated position) and increased the maximum distance of
ambulation (10). A significant correlation was observed
between lower extremity lean body mass per body weight
and symptomatic relief of knee OA (11). We postulated
that without muscular support of the anatomic realign-
ment, patients may retain their previous varus stance
and gait, negating the effect of insole therapy.
In our earlier studies, however, the observation
periods were of only 8 weeks’ duration, and correction of
the femorotibial angle by the insoles was evaluated only
at the baseline assessment. It was uncertain whether the
beneficial effect achieved with use of the insole with
subtalar strapping remained after 8 weeks of use. Here,
we report the results of assessments made at 3 months
and 6 months after the use of a valgus heel wedge and
PATIENTS AND METHODS
Patients with knee OA treated with the traditional
inserted wedged insole and those treated with the lateral-
wedge insert with subtalar strapping were evaluated prospec-
tively. The principal outcome measures were as follows: pain
improvement using a clinical index, the visual analog scale
(VAS) score for subjective knee pain, and radiographic bone
alignment. All subjects had medial compartment knee OA,
according to the American College of Rheumatology criteria
(12), and a standing femorotibial angle of ?176° by radiogra-
phy (the mean ? SD femorotibial angle in standing radio-
graphs in healthy Japanese adult females is 174.6 ? 1.7°; an
angle exceeding 176° is considered to represent a varus de-
formity) (13,14). This study was limited to female subjects,
because men comprise a minority of the population with knee
OA in Japan, and use of the insoles might have been affected
by the subject’s occupation (15). Most Japanese workers wear
shoes outdoors but not inside their office, making the inserted
insole of no use when participants are at work.
The exclusion criteria described by Maillefert et al (16)
were used, and included the following: functional class IV
(according to the Steinbrocker criteria for rheumatoid arthri-
tis) (17), a greater or similar reduction in lateral compared
with medial femorotibial joint space width (concomitance with
lateral knee OA) on plain posteroanterior radiographs, bilat-
eral knee OA, secondary knee OA, hip OA, ankle OA, hallux
rigidus, valgus deformity of the midfoot, other symptomatic
deformity of the foot, advanced arthroplasty of the hindfoot,
any disease treated with insoles, previous ankle arthrodesis,
tibial osteotomy, and intraarticular corticosteroid injection
within 1 month. Patients being treated with a nonsteroidal
antiinflammatory drug (NSAID) for knee OA were not ex-
At baseline, each participant was asked to provide a
history of her use of NSAIDs within the previous week. The
previously used NSAIDs were discontinued, and all partici-
Figure 1. Concept of the lateral-wedge insole with subtalar strapping.
The inserted lateral-wedge insole will not correct a varus deformity of
the knee (a and b), because of the valgus movement at the ankle and
subtalar joints (d). When the talus movement is restricted by the elastic
fixation obtained with tension by a subtalar and ankle joint band (e),
the calcaneal valgus angulation produced by the lateral-wedge insole
will lead to correction of a varus deformity of the knee (c).
3130TODA AND TSUKIMURA
pants were then treated with the same NSAID (acemetacine,
30 mg twice daily) as adjunctive therapy. During the course of
the 6-month study, participants could elect to discontinue the
adjunctive therapy if they had relief of knee pain or experi-
enced adverse effects, including stomachache. The number of
patients in whom adjunctive therapy was discontinued was
assessed at the conclusion of the study.
After providing informed consent, 66 new female
outpatients with knee OA (mean ? SD age 65.6 ? 8.5 years)
seen in our Orthopedic Outcome Clinic from November to
December 2002 were treated with a wedged insole for 6
months. The Orthopedic Outcome Clinic is a private clinic
without an inpatient ward that is known in Japan for providing
conservative therapies for knee OA. Of the 66 participants, 45
lived in Osaka prefecture, where the clinic is located, and 11
(including 8 from Hyogo prefecture and 3 from Kyoto prefec-
ture) lived in neighboring prefectures. All 66 participants could
reach our clinic within 1 hour.
Each symptom relating to knee OA was evaluated
according to the Lequesne index (18). These symptoms in-
cluded the following: 1) pain during nocturnal bed rest with full
extension of the knee, 2) duration of morning stiffness or pain
after getting up, 3) increased pain with standing for 30 minutes,
4) pain on walking, 5) pain when getting up from a sitting
position without the help of arms, 6) maximum distance
walked, 7) ability to climb stairs, 8) ability to descend stairs, 9)
ability to squat, and 10) ability to walk on uneven ground. Both
pain during nocturnal bed rest and pain after awakening were
evaluated by patient self-report, because patients could not be
observed at night or during the early morning. All other
symptoms were assessed under stable conditions (by research
nurses who were uninformed of the objective of the study) at
the commencement of treatment and again at the third and
sixth months thereafter.
Disease duration was based on each patient’s recollec-
tion of the onset of knee pain. Height was measured to the
nearest 1 cm, using a stadiometer, and weight was measured to
the nearest 0.1 kg, with subjects standing erect and wearing
underwear and robes without shoes. Radiographs were evalu-
ated for changes characteristic of OA in anteroposterior views
using the Kellgren/Lawrence (K/L) grade, as described in the
Atlas of Standard Radiographs (19). Initial recordings were
made of age, disease duration, height, weight, the Lequesne
index, the K/L grade, and the degree of bone destruction.
Two types of insoles were prepared: the strapped
insole, comprising a urethane wedge with a 12-mm elevation
(tilt angle 11.2°) that was fixed to an ankle-sprain support
designed to fit around the ankle and subtalar joints (Sofra
Wolfer; Taketora, Tokyo, Japan) (Figure 2A), and a tradi-
tional shoe-inserted insole (Wedge heel supporter; Sanshin-
Kosan, Osaka, Japan), which was a lateral sponge-rubber heel
wedge with a 6.35-mm elevation (tilt angle 5°) (Figure 1B). The
application technique of the strapped heel wedge has been
previously reported (10). The urethane used for the strapped
insole was made of PORON L-24 (Rogers Corporation, Chan-
dler, AZ), had a density of 240 kg/m3, 0.54 MPa pull strength,
115% stretch rate, and 1.8 N/mm rip strength.
The reason that urethane was used for the strapped
insole wedge was that the heel wedge in combination with a
subtalar strap had a more natural form-fit to the sole than did
the insert. Although the ordinary insoles were made of sponge-
rubber, we thought that this material was too hard for use in
the insole with subtalar strapping. For constant routine use, the
12-mm elevation wedged insole with a subtalar strap may be
more comfortable than that used in our previous study (20).
Randomization was performed by date of birth. Par-
ticipants with even numbered dates of birth were treated with
the traditional shoe-inserted insole, and those with odd num-
bered dates of birth were treated with the strapped insole.
Subjects in the strapped-insole group were not informed that
the method of fixation at the ankle joint was thought to be
important or that the insole was a patented device. All
participants who received the insole with subtalar strapping
were unaware that they were receiving a more elaborate
Each participant was instructed to use the insole
whenever wearing shoes, for 3–6 hours each day. Daily wear
was limited by the fact that 59 (89.4%) of 66 participants in this
study were Japanese housewives who remove their shoes in
their home and spend only several hours each day wearing
shoes outside. Of the 7 other subjects (10.6%), 2 had full-time
regular employment, and 5 had part-time employment.
Standing radiographs of the knee joints were obtained
at each assessment. The arms were positioned at 90° of
shoulder flexion, with the hands gripping an adjustable-height
stabilization bar. Participants stood on one leg (insole side) in
the position of full knee extension, standing 1 meter from the
x-ray source, with constant and reproducible foot positioning
(foot map). The x-ray beam was centered on the joint space
and was oriented parallel to the tibial plateau. When the
subject’s posture was stabilized, the roentgenogram was ob-
Figure 2. Construction of the 2 types of lateral-wedge insoles. A, The
strapped insoles consist of an ankle support band with adhesive tape,
and a urethane lateral wedge with an elevation of 12 mm. The ends of
the supporter were twisted into a figure 8 around the ankle and
subtalar joints. The ends were affixed with adhesive tape at the
posterior ankle and subtalar joints. B, The inserted insole consists of a
nylon seat, adhesive tape, and a lateral rubber wedge with an elevation
of 6.35 mm. The insole was inserted into ordinary shoes.
USE OF SUBTALAR-STRAPPED INSOLE DECREASES FEMOROTIBIAL ANGLE 3131
tained (7). For each subject, radiographic analysis was per-
formed with and without use of the insole (Figure 3A).
The femorotibial angle was measured as the angle
formed by the axes of the femur and the tibia, according to the
description by Yasuda and Sasaki (7). A pair of parallel lines
was drawn through the distal one-third of the femur and the
proximal one-third of the tibia. The axes of the femur and tibia
were considered to be the lines connecting the centers of parallel
lines through the femur and tibia, respectively (Figure 3B). We
did not use a long-leg film, because this study was focused on the
change in knee alignment achieved by the insole.
The radiographs were scanned and sent to another
hospital via the Internet. Radiographic assessment of OA
severity and the femorotibial angle was determined by 3
orthopedic surgeons who were blinded to the category of the
subjects. In this study, the mean value of inter/intraobserver
error of femorotibial angle without insoles at baseline (n ? 61)
was 0.16° (95% confidence interval [95% CI] ?0.28, 0.35; P ?
0.83) using a paired t-test (data not shown), when the results of
measurement of femorotibial angles were compared between
interobservers and intraobservers. We believe this methodol-
ogy is reliable for measuring the femorotibial angle.
The Lequesne index score and the VAS score for
subjective knee pain at the third and sixth months were
compared with the baseline recordings in each group. The
urethane wedge or rubber orthotic was replaced every 2 weeks,
and use of the respective insoles was confirmed by visual
inspection of the material for wear. At the conclusion of the
study period, participants were asked whether they hoped to
continue to wear or hoped to discontinue use of the respective
insoles and their impression of the insoles. The rate of
compliance was compared between the 2 groups.
Statistical analysis. The baseline characteristics (dis-
ease duration, height, weight, femorotibial angle, VAS score,
and Lequesne index score) of the 2 groups were compared
using one-way analysis of variance. Radiographic grades, the
number of patients withdrawing from study, the number of
patients using NSAIDs, and compliance were compared using
the chi-square test. A paired t-test was used to assess for
statistically significant differences in the Lequesne index score,
the VAS score, and the femorotibial angle between the
baseline, 3-month, and 6-month assessments in each group. P
values less than 0.05 were considered significant.
Five (7.6%) of the 66 subjects, including 3 in the
strapped-insole group and 2 in the inserted-insole group,
did not complete the study. However, we determined
that the number of dropouts was not significantly differ-
ent between the 2 groups (P ? 0.67). Three patients,
including 1 in the strapped-insole group, were lost to
followup at the 3-month assessment, and 2 subjects in
the strapped-insole group did not return for the 6-month
followup visit (Figure 4).
When the dropouts were interviewed by tele-
phone, 3 of them cited household commitments as the
reason for withdrawal from the study, and 2 had moved.
All dropouts reported an improvement in comparison
with baseline, although the changes in the femorotibial
angle were unknown. During the 6-month study period,
none of the original 66 patients required surgery due to
bone destruction at the knee.
Characteristics of the participants. Of the 61
subjects who completed the study, 29 were in the
strapped-insole group and 32 were in the inserted-insole
group. At the initial assessment, there were no signifi-
cant differences between the groups in age (P ? 0.21),
Figure 3. Method of measuring the femorotibial angle (FTA). A, The
axes of the foot map were drawn perpendicular to the radiographic
film. The femorotibial joint space was marked on adhesive tape and
the x-ray beam centered on the joint space. B, The femorotibial angle,
which is the angle formed by the axes of the distal one-third of the
femur and the proximal one-third of the tibia.
Figure 4. Course of the 6-month randomized trial. OA ? osteoar-
3132 TODA AND TSUKIMURA
disease duration (P ? 0.9), height (P ? 0.54), weight
(P ? 0.97), femorotibial angle (P ? 0.66), VAS score
(P ? 0.75), index of disease severity (P ? 0.89), or
distribution of K/L scores (P ? 0.32) (Table 1). Based on
our observations of material wear, we judged that each
participant used the insole as instructed.
Adjunctive therapy with NSAIDs. Before enroll-
ing in this study, 25 (86.2%) of the 29 participants in the
strapped-insole group and 27 (84.4%) of the 32 partici-
pants in the inserted-insole group took NSAIDs during
the previous 1 week. The rate of NSAID use prior to
screening was not significantly different between the 2
groups (P ? 0.57). At 6 months, 17 patients (58.6%) in
the strapped-insole group and 17 patients (53.1%) in the
inserted-insole group discontinued NSAID use due to
relief of their knee pain (Table 2).
Femorotibial angle. At the 3-month assessment,
the mean (?SD) femorotibial angles, as measured with
the insole inserted, were 180.6 ? 5.8° and 184.1 ? 5.1° in
the strapped- and inserted-insole groups, respectively.
The angle was significantly less at 3 months compared
with baseline in the strapped-insole group (P ? 0.0001)
but not in the inserted-insole group (P ? 0.2). At 6
months, the femorotibial angle in the strapped-insole
group (180.7 ? 5.7°) was significantly lower than that at
baseline (P ? 0.0001), but a significant difference was
not detected in the inserted-insole group (183.7 ? 5.6°;
P ? 0.3) (Figure 5A).
Lequesne index. Compared with the baseline
assessment, the Lequesne index scores in the strapped-
insole group at months 3 and 6 (7.6 ? 5.7 and 7.5 ? 5.8,
respectively) were significantly improved (P ? 0.013 and
P ? 0.033). In the inserted-insole group, there was no
statistically significant difference between the index
score at the 3-month (9.2 ? 5.8) and baseline assess-
ments (P ? 0.14) and between the 6-month (9 ? 5) and
baseline assessments (P ? 0.31) (Figure 5B).
VAS for subjective knee pain. In the strapped-
insole group, the VAS scores at 3 months (33.6 ?
20.3%) and 6 months (32.7 ? 20.7%) were significantly
lower than the baseline score (P ? 0.0001 and P ? 0.001,
respectively). In the inserted-insole group, the VAS
scores were not significantly different between the
3-month (45.3 ? 24%) and baseline assessments (P ?
0.26) and between the 6-month (44.5 ? 20%) and
baseline assessments (P ? 0.36) (Figure 5C). At the
6-month assessment, the VAS scores for 3 (4.9%) of 61
patients decreased to 0%, indicating that they did not
meet the criteria for knee OA through the 6 months of
treatment. All 3 patients were in the strapped-insole
Characteristics of the 61 participants who completed the 6-month study*
at baseline, degrees
score at baseline
VAS score at
Strapped insole (n ? 29)
Mean ? SD
Inserted insole (n ? 32)
Mean ? SD
63.1 ? 7.9
5.7 ? 7.3
154.4 ? 6.1
58.6 ? 8.3
183.4 ? 6
9.7 ? 550 ? 18.7
7.7 ? 11.6
66.4 ? 7.4
5.5 ? 6.5
153.6 ? 6
59 ? 8.1
184.1 ? 5.1
9.9 ? 548.1 ? 20.8
* In the strapped-insole group, 19 patients had a Kellgren/Lawrence (K/L) score of 2, 4 had a K/L score of 3, and 6 had a K/L score of 4. In the
inserted-insole group, 21 patients had a K/L score of 2, 8 had a K/L score of 3, and 3 had a K/L score of 4. VAS ? visual analog scale; 95% CI ?
95% confidence interval.
NSAID use at baseline and during the 6-month study*
(n ? 29)
(n ? 32)
Took NSAIDs during the week before enrollment
Continued NSAIDs during the 6-month study period
Discontinued NSAIDs due to relief of knee pain
Discontinued NSAIDs due to adverse effects†
* Values are the number (%). NSAID ? nonsteroidal antiinflammatory drug.
USE OF SUBTALAR-STRAPPED INSOLE DECREASES FEMOROTIBIAL ANGLE3133
Compliance with insole use. At the conclusion of
the study, 75% of subjects in the inserted-insole group
and 82.8% of those in the strapped-insole group stated
that they hoped to continuously wear their insoles.
There was no significant difference between the 2 groups
in terms of compliance (P ? 0.34). The reasons given for
discontinuing wear of the strapped insole were the
necessity for larger shoes than ordinarily used (n ? 3)
and ineffectiveness (n ? 2). The reasons for discontinu-
ing wear of the inserted insole were ineffectiveness (n ?
4), slipping or instability of shoes (n ? 2), and difficulty
when using many types of footwear, including open-toed
shoes (n ? 2).
In this study, only those participants using the
subtalar strapped insole demonstrated a significantly
decreased femorotibial angle and improved VAS and
Lequesne index scores in comparison with baseline
assessments. This result reflects those of our previous
trial, in which participants using a subtalar strapped
insole had a significantly decreased femorotibial angle
and VAS scores compared with baseline (9). These
results suggest that a subtalar strapped insole maintains
the valgus correction of the femorotibial angle in pa-
tients with varus knee OA for 6 months, indicating a
longer-term clinical improvement.
However, it remains uncertain whether the sub-
talar strapped insole can restrict the progression of varus
deformity of knee OA. Cerejo et al (21) explored the
impact of alignment on subsequent progression of knee
OA according to the baseline stage of disease. These
investigators reported that, “In knees with mild OA (K/L
grade 2), the odds of 18-month progression in the medial
compartment were increased 4-fold by varus alignment
at baseline.” Tohyama et al (22) reported that during
their 9-year study, lateral heel wedges without strapping
had no effect on the progression of radiographic changes
in knee OA.
If use of the insole with subtalar strapping main-
tains valgus correction of the femorotibial angle for ?6
months, the subtalar strapped insole may restrict the
progression of varus deformity of knee OA. We plan to
continue to monitor our subjects for an additional 1–3
years in order to determine the long-term effect of
subtalar strapping. In addition to lower extremity re-
alignment, another advantage of the insole with subtalar
strapping over the inserted insole is its adaptability. The
inserted insoles often slip within the shoes, requiring
frequent repositioning, and are difficult to use when
wearing open-toed shoes, boots, slippers, or high-heeled
shoes. In contrast, the insole with subtalar strapping
does not slip or change position in shoes, and it is
compatible with many types of footwear and can even be
used without shoes.
The disadvantage associated with the strapped
insole is the necessity for shoes more than 1 full size
larger than the shoes ordinarily worn in order to accom-
modate the thickness of the supporter. However, more
detailed data regarding compliance and tolerance
should be assessed in a future study.
In this study, patients with knee OA who used the
inserted insole did not show an improvement in the
femorotibial angle, the VAS score, or the Lequesne
index score at 3 and 6 months compared with their
baseline assessments. It should be noted that the im-
provement in the femorotibial angle observed by Keat-
ing et al (6) resulted from use of a full-length lateral-
wedge insole rather than the lateral heel wedge used in
this study. However, Maillefert et al (16) reported that at
the 1-month, 3-month, and 6-month assessments, the
percentage of patients with knee OA who had an
improved assessment of disease activity and improve-
ment in the Western Ontario and McMaster Universi-
ties [WOMAC] subscales for pain, joint stiffness, and
physical functioning was not significantly different be-
tween those wearing full-length laterally wedged and
those wearing the neutrally wedged insoles without
subtalar strapping. Thus, the efficacy of the inserted
insole without subtalar strapping may be mild for pa-
tients with knee OA.
Although in this study use of the inserted insole
did not demonstrate a significant effect on the femo-
Figure 5. Comparison of the femorotibial angle (A), Lequesne index
score (B), and visual analog scale score (C) at baseline, month 3, and
3134 TODA AND TSUKIMURA
rotibial angle, VAS score, or Lequesne index score, 17
subjects (53.1%) in the inserted insole group discontin-
ued NSAID use due to alleviation of knee pain. Pham et
al (23) reported that in their 2-year prospective study,
the number of days during which subjects took NSAIDs
was lower in the group with inserted laterally wedged
insoles than in the group assigned to neutrally wedged
insoles. Thus, there is evidence that the inserted insole
can also be helpful in improving knee pain in patients
with medial knee OA.
The current study did not include a control group
of subjects treated only with the NSAID and a placebo
insole. Such a group would enable a clearer evaluation
of the effect of the NSAID. We recently compared the
efficacy of an insole with subtalar strapping (n ? 23) and
subtalar strapping without an insole (placebo; n ? 22) in
a 4-week prospective study, in which all participants
were also treated with NSAIDs (24). In the strapped-
insole group, the Lequesne index score (?3.7 ? 2.6) was
significantly improved compared with that in the placebo
insole group (?1 ? 3.7; P ? 0.033). We believe that in
that study, the efficacy of the subtalar strapped insole
was not dependent on the effect of the NSAIDs.
In the current study, the material used to make
the insole (sponge-rubber or urethane) was different in
the inserted-insole and strapped-insole groups. We pre-
viously assessed the symptomatic effects associated with
use of a urethane insole with a 12-mm elevation and
those associated with use of a sponge-rubber insert with
subtalar strapping (25). In that study, the Lequesne
index score was significantly improved in the urethane-
insole group (n ? 36) compared with that in the
rubber-insole group (n ? 37) (P ? 0.007). Adverse
effects were more common in the rubber-insole group
(14 of 37 [37.8%]) than in the urethane-insole group (5
of 36 [13.9%]); this difference was statistically significant
(P ? 0.032). The most common side effect among
subjects in the rubber-insole group was foot pain (7 of 14
[50%]). Thus, we inferred that an insole with subtalar
strapping composed of rubber sponge was not comfort-
able to use for 6 months in the current study.
If in our previous study (25) the height of the
inserted insole had been increased to 12 mm (tilt angle
1.2°), the same elevation as that of the subtalar strapped
insole, the results for femorotibial angle correction
might have been different from those in the current
study. However, Kerrigan et al (26) reported that in their
study, all subjects were comfortable wearing the 5°
wedged insoles. In that study, nearly every subject
reported varying degrees of mild discomfort while wear-
ing the 10° wedge, stating that their feet felt somewhat
cramped inside their shoes. According to these reports,
we used the sponge-rubber inserted insole with eleva-
tions of 6.35 mm (tilt angle 5°) as an optimal height.
In our previous study, the femorotibial angle was
decreased after wearing the insole in 34 (81%) of 42
patients with varus deformity knee OA in the strapped-
insole group and in 17 (37%) of 46 patients in the
inserted-insole (without subtalar strapping) group (10).
However, 8 (19%) of 42 patients in the strapped-insole
group did not demonstrate a change in the angle, which
seemed to be rigid. Future study should clarify the
implications of the correlation between rigidity of the
femorotibial angle and use of the strapped insole.
Disadvantages associated with use of the
strapped insole included decreased freedom of the ankle
joint and increased pain with ambulation on uneven
ground (10). Although patients with a history of ankle
disorders were excluded from this study, the insole was
predicted to be unsuitable for patients with concomitant
ankle disorders, including ankle OA.
In this study, we used the Lequesne index for
the assessment. The 8 items in the index, excluding
pain during nocturnal bedrest and pain after awakening,
were assessed under stable conditions in our clinic.
The rationale for using this index was that the number
of items was less than that in other indices (including the
WOMAC index), and the items were relatively easy for
the participants to demonstrate under objective obser-
vation when they presented to our clinic, although the
index was considered to assess function rather than pain.
Standing full-length radiographs that included
the hip and ankle joints might have been necessary for
the measurement of the knee alignment in this study.
According to Koshino (14), however, obtaining standing
full-length radiographs requires a precise instrument or
high-quality technique and increased radiation to a
larger area of the patient’s body. When measuring the
femorotibial angle only, obtaining standing, compara-
tively short-length radiographs that include the mid-
thigh and mid-calf would be conventional clinically (14).
The current study was limited in that it did not
determine the duration of insole wear each day. Consid-
ering the duration of shoe-wearing, the inserted insole
should have been used for 3–6 hours daily. Our obser-
vations of the insole material allowed us to detect
whether patients did not use the insole. We also could
recognize when participants wore the strapped insole
without shoes, because part of the support (that which
makes contact with the floor) was more soiled than it
would be if the subject were wearing shoes. However, it
will be necessary to consider the reliability of these
USE OF SUBTALAR-STRAPPED INSOLE DECREASES FEMOROTIBIAL ANGLE3135
measures in a future study. In this study, a completely
randomized and controlled trial was difficult; random-
ization using date of birth was simple, but the investiga-
tors were aware of the group to which each subjects had
been assigned. Future studies should be completely
randomized and controlled.
Concerning the study design, an intent-to-treat
analysis was performed for adjunctive therapy with
NSAIDs. Every participant could discontinue adjunctive
therapy because of relief of their knee pain or adverse
effects, including stomachache. However, the effects of
insoles were not assessed by an intent-to-treat analysis,
and all participants were instructed to use their respec-
tive insoles for 6 months. We are planning a study in
which every participant can decide to discontinue use of
Another possible limitation of this study was the
inability to assess the correlation between the efficacy of
the insole with subtalar strapping and the radiographic
severity of knee OA. This limitation was secondary to
the relative paucity of participants with a K/L score of 4
(n ? 9). It will be necessary to study this in a larger
number of subjects with advanced knee OA.
The prevalence of knee OA in our society is
increasing due to the escalating proportion of elderly
persons. A conservative therapy such as use of an insole
that provides a low-cost, effective complement or alter-
native to surgical treatment would be a very useful
adjunct to the care of patients with knee OA and would
benefit the health care economy.
We thank Dr. Neil Segal (Department of Orthopedics
and Rehabilitation, University of Iowa Health Care) for his
advice. We also thank Dr. Nancy Lord Johnson, a patent
attorney and medical doctor, of Nancy Lord Johnson, Ltd., for
her helpful suggestions as a native English speaker.
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3136TODA AND TSUKIMURA