©Journal of Sports Science and Medicine (2008) 7, 480-485
Received: 28 April 2008 / Accepted: 10 September 2008 / Published (online): 01 December 2008
Position-specific deficit of joint position sense in ankles with chronic functional
Shigeki Yokoyama 1??, Nobuou Matsusaka 2, Kazuyoshi Gamada 3, Makoto Ozaki 1 and Hiroyuki
1 Department of Orthopaedic Surgery, Graduate School of Medicine, Nagasaki University, Nagasaki, Japan
2 Department of Health Sciences, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan,
3 Department of Physical Therapy, Faculty of Health Sciences, Hiroshima international University, Hiroshima, Japan
The present study was aimed to test a hypothesis that individuals
with functional ankle instability (FAI) underestimate the joint
angle at greater plantarflexion and inversion. Seventeen males
with unilateral FAI and 17 controls (males without FAI) con-
sented for participation in this IRB-approved, case-control
study. Using a passive reproduction test, we assessed ankle joint
position sense (JPS) for test positions between 30 and -10 de-
grees plantarflexion with an inclement of 10 degrees with or
without 20° inversion at each plantarflexion angle. The constant
error (CE) was defined as the value obtained by subtracting the
true angle of a test position from the corresponding perceived
angle. At plantarflexed and inverted test positions, the CE values
were smaller in negative with greater in the FAI group than in
the control group. That is, in the FAI group, the FAI group
underestimated the true plantarflexion angle at combined 30°
plantarflexion and 20° inversion. We conclude that the ankle
with FAI underestimate the amount of plantarflexion, which
increases the chance of reaching greater planterflexion and
inversion than patients’ intention at high risk situations of
spraining such as landing.
Key words: Functional ankle instability, lateral ankle sprain,
proprioception, joint position sense, constant error.
Lateral ankle sprain (LAS) is among the most common
injuries in sports (Jackson et al., 1974; Han and Mu-
wanga, 1990; Wilkerson, 1992), accounting for 15-30%
of all sports injuries (Garrick and Requa, 1988; Adamson
and Cymet, 1997). More than 23,000 LAS’s have been
estimated to occur daily in the United States, which
equates to one sprain per 10,000 people (Kannus and
Renstrom, 1991; Soboroff et al., 1984) reported that the
cost of treating these injuries ranged from $318 to $914
per sprain, with an annual aggregate cost in the United
States of $2 billion. The recurrence rate of LAS among
athletes has been reported to be as high as 70-80% (Smith
and Reischl, 1986; Yeung et al., 1994). Functional ankle
instability (FAI) is a sequelae frequently associated with
acute inversion ankle sprains and was first described by
Freeman (Freeman, 1965). Functional ankle instability
(FAI) is characterized by recurrent ankle sprains and
sensations of “giving way” at the ankle joint during
physical activity with or without mechanical instability
(Freeman, 1965; Goldie et al., 1994; Tropp et al., 1985).
FAI becomes evident in 10 to 60% of the patients with an
acute ankle injury (Itay et al., 1982; Peters et al., 1991).
A few studies have proposed, as a possible cause of
FAI, mechanical instability (Freeman, 1965, Lentell et al.,
1995), weakness of the peroneal muscles (Tropp, 1986;
Wilkerson et al., 1997) and proprioceptive deficit (Boyle
and Negus, 1998; Glencross and Thornton, 1981; Kon-
radsen and Ravn, 1990; Tropp et al., 1984; Willems et al.,
2002). The role of FAI on proprioceptive deficit is con-
troversial; a few studies proposed that FAI negatively
affects joint position sense (JPS) (Boyle and Negus, 1998;
Glencross and Thornton, 1981, Jerosch and Bichof,
1996), while others denied it (Gross, 1987; Holme et al.,
1999). Furthermore, previous studies showed mixed re-
sults regarding the direction of error in JPS: Willems et al.
(2002) claimed that the error was usually negative and
that all subjects (both healthy subjects and those with
ankle instability) tended to underestimate the test position.
In contrast, Feuerbach et al. (1994) found that the exact
error was not significantly different from zero for subjects
without injuries. Thus, there exists a clear knowledge gap
as to whether or not recurrent ankle sprain in FAI is asso-
ciated with underestimation of the joint position. If indi-
viduals with FAI underestimate the joint position, they
may place their foot and ankle joints into greater plantar
flexion and inversion positions than they perceive. This
misperception may place the ankle joint in a vulnerable
position that increases the risk of reinjury during activity.
Most LAS occur during foot contact on landing or
locomotion associated with either unanticipated foot
placement on a sloped surface (e.g. someone’s foot) or
inappropriate positioning of the foot in space before foot-
contact with the surface (Robbins and Waked, 1998). In
both cases, humans perceive the amplitude of inversion
less than the true position (Bahr et al., 1994; Robbins et
al., 1995). In addition, excessive inversion and plantar-
flexion at the landing are considered a major cause of
LAS (Tropp et al., 1985; Wright et al., 2000). If individu-
als with FAI do tend to underestimate the joint position,
the ankle may be placed into a high risk position or a
greater plantarflexed and inverted position than it actually
The present study was aimed to test a hypothesis
that individuals with functional ankle instability (FAI)
underestimate the joint angle at greater plantarflexion and
inversion as compared with healthy individuals. The re-
sults of this study will lead us to understand JPS deficits
Yokoyama et al.
in FAI more clearly as to the direction of the joint posi-
tion error. This case control study will test the hypothesis
by comparing the direction and amount of error in JPS
between FAI and healthy groups.
The study protocol was approved by the Ethics Commit-
tee of the Nagasaki University School of Health Sciences.
Participants were recruited at local clinics and the Univer-
sity campus. All subjects were informed of the procedures
and signed an approved consent form prior to the enrol-
Inclusion criteria for the FAI group were: (1) males
aged between 18 and 22, (2) at least one episode of major
inversion sprain (Grade II or more severe) of the right
ankle, followed by (a) subsequent difficulty in standing
on the right foot immediately following the injury; and (b)
recurrent sprains (more than 3 times) of the right ankle
and continuous feeling of “giving way” in daily activities
or during exercises. Exclusion criteria for the FAI group
were: (1) any pain or stiffness in the right ankle during the
previous three-month period of the testing, (2) positive
result in the manual anterior drawer test or the inversion
stress test, (3) general joint laxity, (4) any medical prob-
lems, (5) communication disturbance or mental disorder.
Seventeen FAI patients (19.6 ± 2.1ys, 1.73 ± 0.08m, 66.4
± 8.0kg) agreed on participating in this study after com-
pleting a screening questionnaire. The following signs
were used to assess generalized joint laxity (GJL): pas-
sively dorsiflex the 5th metacarpophalangeal joint to ≥90°,
Oppose the thumb to the volar aspect of the ipisilateral
forearm, hyperextend elbow to ≥10°, hyperextend knee to
≥10°, and place hands flat on the floor without bending
the knees. Participants were considered to have general-
ized joint laxity (GJL) if they had at least four of these
nine signs unilaterally or bilaterally (Beighton et al.,
1973) . GJL score of FAI group was 4-8 points (mean ±
SD; 5.1 ± 1.1).
Selection criteria for the control group were: (1)
male with the case matched by age, height and body mass,
(2) current medical problems, (3) no episode of sprain in
the right ankle, (4) no unstable feeling of the right ankle,
(5) absence of pain or stiffness in the right ankle during
the previous three-month period of the testing. (6) any
medical problems, (7) communication disturbance or
mental disorder. Seventeen healthy individuals (20.4 ±
2.3ys, 1.71 ± 0.08m, 65.7 ± 9.7kg) agreed on participating
in this study.
Ankle joint angles were measured using a custom meas-
urement device called "3D ankle position analysis system
(3D-APAS) (Kang et al., 2003) (Figure 1)", comprising
two digital cameras (Canon, PowerShot G5) and an angle
measurement system. The digital camera is commercially
available and the sampling rate was 25Hz. No data reduc-
tion or smoothing was utilized. The angle measurement
system was attached on the platform and provides ana-
logue data of the platform orientation which was used
during validation and experimental measurements. A
custom computer program was coded using Microsoft
excel 2003 that minimize measurement errors and biases
from image distortion as well as camera distance and
Figure 1. 3D ankle position analysis system. Measurements
system using two digital cameras and a platform that allowa
dorsiflexion, palantarflexion and inversion of the ankle.
The 3D-APAS was designed so that the axes of the
testing device for planterflexion/dorsiflexion as well as
inversion/eversion were designed so that the translation of
the leg was minimal during passive ankle joint motion.
The camera images allowed us to observe how far the
lower leg moved during testing and we could not confirm
that there were significant shank translations during the
experiments. It was designed to stabilize the foot with the
anatomical ankle position, which is equivalent to the
ankle position during standing, was utilized as an initial
testing ankle position. In addition, the 3D-APAS allows
for locking the platform at 10 target positions utilized
during the experiments.
Participants were placed in a seated position on a bench
with the knees flexed at 90° and the lower leg positioned
vertically. Before the testing, the long axis of the lower
leg was placed perpendicular to the ground. During test-
ing, the participants’ eyes were covered to eliminate any
visual influence and their foot were bare. The lower leg
was not immobilized during the test in order to minimize
stimulus to the skin of the lower leg (Lentell et al., 1995;
Lephart et al., 1998). The right foot was positioned and
foot was placed on the platform of the ankle position
measurement device with an abduction angle of 15°, so
that the axis of rotation for inversion/eversion of the sub-
talar joint was aligned with the longitudinal axis of rota-
tion of the platform and the excursion of the lower leg
during passive ankle motion was minimal.
Once the foot and ankle were positioned and stabi-
lized on the platform, two markers (a) and (b) on the
lateral side of the participant’s lower leg and three mark-
ers (c), (d) and (e) on the platform were placed (Figure 2).
The ankle planterflexion angle was defined as an angle
between a line connecting markers (a) and (b) and a plane
defined by the markers (c), (d) and (e). The two cameras
Position-specific deficit of JPS in FAI
were placed as far as possible to minimize camera distor-
tion and capture all the markers within the central 2/3 of
Figure 2. Positions of markers on the right foot and the
platform. (a) head of the fibula, (b) lateral malleolus, (c) on
the mid-line of the platform anterior to the toes, (d) on the
medial edge of the platform anterior to the toes, (e) on the
medial edge of the platform medial to the 1st MP joint.
Measurements of JPS during dorsiflexion and plantarflex-
ion with or without inversion of 20° were performed. To
eliminate the learning effects, the order of ankle positions
were randomly selected from the 10 ankle positions; five
plantarflexion angles between 30° and -10° with 10° in-
tervals two inversion angles of 0° and 20°. First, the
participant’s ankle was held in one of the 10 test positions
for 15 seconds. Then, the ankle joint was passively dorsi-
flexed until it reached 10° of dorsiflexion, then rested for
10 seconds. After this, the examiner manoeuvred the
platform to return it at an angular velocity of 2-3° per
second toward the original test position. This angular
velocity was determined based on the literature (Gross,
1987; Willems et al., 2002) and the examiner practiced to
maintain the designated angular velocity. Participants
were instructed to say “stop” when the ankle reached the
position where they thought was the original test position.
The foot position at this point was photographed using the
two digital cameras of the ankle position analysis system.
One measurement for each test position was performed
per each participant. In addition, subjects were not al-
lowed to practice any of the testing position prior to the
Computerised three-dimensional analysis was performed
to compute the participants’ ankle positions using the
images obtained using the two digital cameras. We ob-
tained 3 dimensional coordinates of five markers (a)
through (e) for each testing position. Then, the ankle
position formed by the lines connecting markers (a) and
(b) and the plane defined by markers (c), (d) and (e) was
computed. The author defined the angle between the lon-
gitudinal axis of the lower leg and the platform in the
saggital plane as plantarflexion angle of the ankle. For
each test position, the angle calculated from the digital
image is hereafter referred to as the “estimate angle” (i.e.
the angle perceived by the participant). The value ob-
tained by subtracting the correct angle provided by the
hardware-locked position from the corresponding esti-
mate angle was defined as the constant error (CE). When
the estimated angle is in reduced plantarflexion compared
with the correct angle, the CE was in negative. Analyses
of the angles from the images were performed three times
for each condition by a blinded examiner. An average for
each condition was then calculated from these measure-
A preliminary study was performed to examine reliability
of the measurement method. Three examiners measured
joint position angle of -10°, 0°, 10°, 20° and 30° of plan-
tarflexion at 0° and 20° of the ankle inversion, respec-
tively. The platform of testing device was paced at the
testing angles using hardware fixture, providing exactly
the same and known platform positions. Each measure-
ment was then repeated 3 times to calculate intra-and
inter-rate reliability. The result showed that inter-rater
reliability was good with ICC(3,3) and SEM resulted in
0.917, 0.50° , respectively for the joint position at 0° of
inversion, and 0.747, 1.1°, respectively, at 20° of inver-
sion. Similarly, ICC(1,3) of 0.825 and SEM of 1.05° for
the joint position angles of plantarflexion at 0° of inver-
sion, and ICC(1,3) of 0.624 and SEM of 1.07° at 20° of
inversion for intra-rater reliability.
The accuracy and precision of the measurement
system using 3D-APAS were obtained from the angles of
the platform using the hardware fixture designed to lock
the apparatus at exact 10 testing positions. Accuracy and
precision of the testing device was within 2o and 3o, re-
All data were analyzed using SPSS for windows, version
10.0J (SPSS Inc, Chicago, IL). A three-way analysis of
variance (ANOVA) for split-plot design was performed
with group (FAI or healthy), inversion positions (0 and
20°), plantarflexion angles (-10, 0, 10, 20 and 30°). For
significant main effects, the Tukey Honestly Significant
Difference (HSD) post hoc test was used for pairwise
comparisons. The level of statistical significance was set
at p = 0.05. A priori power analysis was not performed
due to a lack of reasonable assumptions for constant er-
rors in different joint positions.
Three-way ANOVA revealed that there were no signifi-
cant three-way interactions (Table 1). There was
significant two-way interaction between group and
Yokoyama et al.
Table 1. A summary table of 3 way analysis of variance.
PF= plantarflexion, Inv. = inversion, F = Fvalue, p = probability, ES = effect size.
plantarflexion angle (Table1). Tukey's HSD post hoc
analysis revealed that the CE at 30° for 0° and 20° of
inversion , respectively, when comparing CE between two
conditions within FAI group date (p < 0.05 and p < 0.001,
respectively) (Table 2). No significant differences were
detected at any other pairwise comparisons (p > 0.128 and
p > 0.131, respectively).
There was significant two-way interaction between
group and inversion position (Table 1). Post hoc analysis
showed there was significant difference in CE between 0°
and 20° of ankle inversion for the FAI group, while no
significant difference was observed for the control group.
In addition, there were no significant difference in CE at
0° and 20° ankle inversion , respectively, between the FAI
and control group (p > 0.220).
Significant effects of group, inversion position, and
plantarflexion angle were noted, indicating that all of
these factors affect the CE value (Table 1). These findings
indicate that individuals in the FAI group were more
likely to underestimate the plantarflexion angles than
healthy individuals when the ankle was inverted and plan-
All 17 subjects in FAI group demonstrated diffi-
culty standing on one foot and having experienced recur-
rent ankle sprain and giving way. Post-hoc power analysis
for repeated measure ANOVA showed that the power
exceeded 0.8 for intra-, inter-groups as well as mixed
The aim of this study was to determine if patients with
FAI underestimate the joint position when the ankle is
placed in plantarflexion and inversion. The main findings
of this study were that at plantarflexion 30°/inversion 20°,
the FAI group underestimated the plantarflexion angle by
a greater margin than the control group. Therefore, the
study hypothesis was supported by the results of this
study. This positive result suggests that the ankle position
may be in greater planterflexion and inversion than the
The results of the present study are partially consis-
tent with previous studies (Boyle and Negus, 1998;
Feuerbach et al., 1994; Glencross and Thornton, 1981;
Gross, 1987; Holme et al., 1999; Jerosch and Bichof,
1996). Glencross and Thornton (1981) reported signifi-
Table 2. CE according to palantarflexion angle of the ankle. Data are means (±SD).
Ankle Position -10
FAI Inversion 0° .9 (2.6) ***
Inversion 20° .6 (3.2) ***
Control Inversion 0° -.7 (2.9)
Inversion 20° .0 (2.9) ***
*, **, *** denote p < 0.05, p < 0.01 and p < 0.001, respectively, compared with palantarflexion 30°.
cantly greater JPS errors as well as reduced ability of
detecting active movement in the FAI compared with the
uninvolved ankle. In the passive angle-reproduction test
for ankle joint inversion, Jerosch and Bichof (1996) found
that the estimate errors of individuals with FAI were sig-
nificantly greater compared with the control. Boyle and
Negus (1998) assessed the inversion JPS error for inverted
ankles, and found that the JPS error was greater in the
FAI group than in the healthy controls at all positions. On
the other hand, Gross (1987) found no difference in the
absolute values of the error of ankle inversion JPS be-
tween joints with and without FAI. Holme et al. (1999)
failed to reveal any significant differences between in-
jured and uninjured ankles in either active or passive joint
position sense. Feuerbach et al. (1994) found that the
exact error was not significantly different from zero for
subjects without injuries. The result of the present study
suggests the FAI plays a role in affecting proprioception
of the ankle negatively only at combined plantarflexion
30° and inversion 20°.
Underestimation of joint position in FAI has been
reported for both FAI and healthy ankles. Robbins, et al.
(1995) reported greater underestimation of the joint posi-
tion at greater plantarflexion in healthy ankles. Willems et
al. (2002) similarly reported underestimation for both FAI
and control groups when the ankle is in inversion. In
contrast, the present study demonstrated a clear underes-
timation for the FAI group only with greater plantarflex-
ion and inversion. Possible causes of underestimation may
include disturbance of proprioception (Boyle and Negus,
1998; Glencross and Konradsen and Ravn, 1990, Tropp et
al., 1984; Willems et al., 2002), decreased tension of
peroneal muscles (Tropp, 1986; Wilkerson et al., 1997)
and abnormal joint kinematics of both talo-crural and
talo-calcaneal joints (Freeman, 1965; Lentell et al., 1995).
Mechanoreceptors in ligaments and joint capsule, particu-
larly the anterior talofibular ligament (ATFL), may be
damaged during ankle sprain (Freeman, 1965; Saunders,
1980; Renstrom and Konradsen, 1997). The peroneal
muscles reportedly suffer from proprioception deficits,
weakness and the delay of the reaction time (Konradsen
and Ravn, 1990; Tropp, 1986; Willems et al., 2002;
Wilkerson et al., 1997). Furthermore, the lack of the af-
ferent input from the joints may be caused by abnormal
kinematics in FAI. For the knee joint, ACL deficient
knees demonstrated greater deficit in JPS than ACL
0 10 20 30
-.6 (2.6) ***
-.1 (4.0) *** -2.9 (2.8) *** -2.8 (3.3) ***
-.2 (3.1) -.9 (2.6)
.5 (2.1) *** .2 (2.9) ***
-1.6 (3.9) * -.8 (3.5) ** -5.0 (3.0)
-.6 (3.1) ***
Position-specific deficit of JPS in FAI
reconstructed knees, which suggests that abnormal joint
kinematics have a negative impact on JPS (Reider et al.,
2003). Therefore, there is a need for more accurate kine-
matic studies to reveal abnormal ankle kinematics associ-
ate with FAI that may affect proprioception.
The present study was carefully designed to elimi-
nate potential biases. First, the testing device, “3D ankle
position analysis system” was designed so that the shank
and above receives no skin sensation or any other me-
chanical input directly from the device. The measurement
error of this device was less than 3°. This may have con-
tributed to the smaller CE smaller than 3° in healthy sub-
jects at 0° inversion as compared with the CE of 9-10°
reported by Robbins et al. (1995). Second, strict selection
criteria were utilized to eliminate potential confounding
factors including aging, hormones, general joint laxity,
and mechanical ankle instability. This should have al-
lowed us to evaluate the role of FAI on proprioception. A
post hoc power analyses revealed that the statistical power
exceeded 0.80 when the CE value at combined plantar-
flexion 30° and inversion 20° in FAI group is compared
with the control group for the inter-group comparison or
the value at plantarflexion 20° with inversion 20° for the
intra-group comparison. We utilized CE as indices for the
assessment of proprioception and we believe the CE pro-
vides valuable information with regard to the overestima-
tion and underestimation of the joint positions (Willems
et al., 2002).
Generalizability of this study would not be limited
to our study population of young, healthy individuals. JPS
is affected negatively that error in JPS increases by 3º as
age increases (Robbins et al., 1995), whereas the present
study detected greater than 9° of underestimation for the
FAI group. However, the present study would not be
generalized conclusively to the individuals with general
joint laxity who potentially have mechanical instability of
the ankle joint, as a conclusion has not been reached as to
the possible association between mechanical instability
and functional instability (Richie, 2001). Another aspect
of the limited generalizability is the static nature of this
testing procedure. However, present study supports the
idea that the joint position is underestimated at plantar-
flexion 30°/inversion 20° and the ankle joint may be at
greater platnerflexion and inversion at landing. Consider-
ing landing with the ankle inversion and plantarflexion is
the major cause of ankle sprain in sports (Tropp et al.,
1985; Wright et al., 2000), revealing the mechanism of
underestimation at plantarflexion and inversion would be
the next step in this topic.
The strengths of this study lie in the high accuracy
and reproducibility of the data produced by the measure-
ment system, the careful performance of the examination
procedures in accordance with approaches used in previ-
ous studies, and the low risk of measurement and selec-
tion bias. Statistical power was considered strong for the
major results. Subjects were not allowed to practice prior
to the testing which might have increased variability of
the measurements. However, randomization of the testing
procedure, sufficient statistical power and high intra-tester
repeatability should have minimized the ordering bias.
Weakness of this study would include insufficient statisti-
cal power to detect the differences between the positions
of plantarflexion 30°/inversion 20° and plantarflexion
30°/inversion 0°, which may highlight the role inversion
on the proprioceptive deficit.
The present study revealed underestimation of an-
kle joint position exists in FAI group at greater plantar-
flexion/inversion. Proprioceptive training may be useful
for secondary prevention for patients with FAI after ankle
sprain (Handoll et al., 2001; Michell et al., 2006; Wester
et al., 1996). The authors suggest the accurate kinematic
studies to reveal the mechanism of underestimation in
FAI (Reider et al., 2003).
In the present study, we aimed to determine the effects of
FAI on ankle JPS. We conclude that subjects with FAI
underestimated the amount of plantarflexion. Future study
may include accurate analyses of ankle kinematics to
identify possible causes of underestimation.
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• Joint position sense (JPS) of the ankle with func-
tional ankle instability was investigated utilizing a
passive reproduction test.
• The FAI group demonstrated greater error of the
joint position than the control group only when the
ankle was positioned at combined inversion and
• The FAI group underestimated plantarflexion angle
when the ankle was placed at combined inversion
PhD student, Department of Orthopaedic Surgery, Graduate
School of Medicine, Nagasaki University.
Biomechanics, athletic rehabilitation, motion analysis.
Professor, Department of Orthopaedic Surgery, Graduate
School of Medicine, Nagasaki University.
Associate Professor, Department of Physical Therapy, Hi-
roshima International University.
Department of Orthopaedic Surgery, Graduate School of
Medicine, Nagasaki University
Professor, Department of Orthopaedic Surgery, Graduate
School of Medicine, Nagasaki University
?? Shigeki Yokoyama
8 Iga-machi, Takahashi-city, Okayama, 716-8508, Japan.