The Relationship Between Forefoot, Midfoot, and Rearfoot Static

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					   Journal of Orthopaedic & Sports Physical Therapy
   Official Publication of the Orthopaedic and Sports Physical Therapy Sections of the American Physical Therapy Association




The Relationship Between Forefoot,
Midfoot, and Rearfoot Static Alignment in
Pain-Free Individuals
Kirsten Rossner Buchanan, PT, PhD, ATC 1
Irene Davis, PT, PhD 2



Study Design: Correlational study.
Objectives: To determine whether, and to what degree, a relationship exists between forefoot
                                                                                                         and/or subtalar joint through ex-
angle and weight-bearing midfoot and rearfoot position.                                                  cessive pronation. Much of the
Background: There have been conflicting reports with regard to the degree to which the structure         foundation for orthotic interven-
of the foot may influence the function. The influence of forefoot structure on weight-bearing            tion is based on Root’s theories.
midfoot and rearfoot position has not been extensively investigated.                                     Aside from Root’s hypothesis that




                                                                                                                                                   RESEARCH
Methods and Measures: Fifty-one healthy subjects participated in this study (26 male and 25              forefoot varus is abnormal, there is
female). Forefoot angle was measured in prone as varus (positive numbers), neutral (0), or valgus        no consistent body of research that
(negative numbers). Navicular drop was measured from subtalar joint neutral to unilateral standing
                                                                                                         speaks to how static foot measures
relaxed. Rearfoot angle was measured in relaxed single-limb stance as the angle between a line
that bisected the calcaneus and a line that bisected the lower third of the leg. The relationships       relate to one another. Recent stud-
between forefoot angle and navicular drop, and between forefoot angle and relaxed rearfoot               ies have suggested that a certain
angle, were investigated. The same relationships were also investigated in the neutral forefoot          amount of forefoot varus or valgus
subgroup when the sample was divided in 3 subgroups based on 1 standard deviation of forefoot            may be normal in an adult popula-
angle.                                                                                                   tion.6,8 Additionally, others re-




                                                                                                                                                   REPORT
Results: There is a significant relationship between forefoot angle and relaxed rearfoot angle (r =      ported no relationship between
0.52, P .001), as well as between forefoot angle and navicular drop (r = 0.55, P .001), in the
                                                                                                         static measures of the forefoot and
whole sample (n = 51). Average degrees of forefoot angle in the neutral subgroup (between 1.0°
and 8° of varus) are not associated with predictable positions of relaxed rearfoot angle (r = 0.19, P    rearfoot position or motion.16,18
= .24) or navicular drop (r = 0.01, P = .96).                                                               While rearfoot motion during
Conclusions: Based on the results of this study, there is a significant relationship between forefoot    gait has received much attention
angle and relaxed rearfoot angle, as well as between forefoot angle and navicular drop, in healthy       in the literature,11,18,23,26 few stud-
subjects. These relationships were not found when forefoot varus values were within a standard           ies have addressed the relationship
deviation of the sample mean. J Orthop Sports Phys Ther 2005;35:559-566.                                 between forefoot alignment and
Key Words: biomechanics, foot position, pronation, subtalar joint                                        weight-bearing midfoot and rear-
                                                                                                         foot position. McPoil et al16 as-




T
                  he relationship between the structure of the foot and its sessed the relationship between
                  function is not well understood. Malalignments in structure the static measures of forefoot po-
                  of the forefoot, midfoot, and rearfoot are thought to lead to sition, navicular drop, and dy-
                  compensatory motion, which may ultimately result in injury. namic rearfoot motion. They
                  Root et al22 suggested that the forefoot should be aligned found these static measures not to
perpendicular to the bisection of the calcaneus when the foot was in be predictive of rearfoot motion.16
subtalar joint neutral. Any deviation from this position, either varus or However, they recognized that in
valgus, was considered abnormal and could lead to abnormal motion their study the low sample size
and potential injury. Root et al22 also suggested that individuals with a
                                                                                                         used for the number of static vari-
forefoot varus alignment might compensate through the midtarsal
                                                                                                         ables measured could have limited
1
                                                                                                         their statistical power.16 Mueller et
  Biomechanical Consultant, Sports Medicine Dept, Maine Medical Center, Portland, ME; Owner, Impact
Sports Medicine, LLC, Falmouth, ME.
                                                                                                         al18 studied the relationships be-
2
  Director of Research, Drayer Physical Therapy Institute, University of Delaware, Newark, DE; Associate tween forefoot position, navicular
Professor, Department of Physical Therapy, University of Delaware, Newark, DE.                           drop, and rearfoot angle in
The protocol for this study was approved by The University of Virginia Institutional Review Board.
Address correspondence to Kirsten Rossner Buchanan, Impact Sports Medicine, LLC, 21 Twin Ponds subtalar joint neutral position.
Drive, Falmouth, ME 04105. E-mail: info@impactsportsmedicine.com                                         They found a significant relation-

Journal of Orthopaedic & Sports Physical Therapy                                                                                            559
ship between forefoot position and navicular drop (r      The subject walked around the clinic for approxi- the
= 0.29-0.33), but no relationship between forefoot
position and rearfoot angle in subtalar joint neutral.
This is not surprising, as the subtalar joint neutral
position does not provide information regarding the
amount of frontal plane compensation the rearfoot
may exhibit in relaxed stance.
   Static forefoot, midfoot, and rearfoot measures are
presumed to be related to dynamic measures of
pronation. Research suggests that excessive pronation
is associated with pathology.1,20,25 Despite the sparse
information regarding the relationship between fore-
foot structure and midfoot/rearfoot pronation in a
normal population, clinicians often use structural
forefoot measures as a basis for intervention in
patients with pathology. Orthotic intervention today
is an example. Much of the orthotic evaluation and
intervention today is based on Root’s theory regard-
ing relationships between forefoot alignment and
midfoot/rearfoot compensation.22 For example, a
patient with forefoot varus and an associated increase
in midfoot and/or rearfoot pronation would be
prescribed an orthotic with a medial forefoot post to
balance the foot. This accommodation of the forefoot
varus with a medial post is believed to decrease the
need for compensatory midfoot and rearfoot motion.
Forefoot measures are assumed to be related to
midfoot and rearfoot measures based on Root’s             FIGURE 1. Prone position for marking the leg and calcaneus.
theory, but this has not been clearly established.
Therefore, the purpose of this study was to investigate   5 minutes and all marks were then redrawn. A second
the relationship between static forefoot angle and        averaged set of 3 measurements for each static foot
associated positions in the midfoot and rearfoot          position was performed to determine intratester reli-
during stance. It was hypothesized that as forefoot
                                                          ability. An intraclass correlation coefficient (ICC3,3)
varus increased, navicular drop and calcaneal ever-
                                                          was used to quantify intrarater reliability for these 19
sion would also increase. It was also hypothesized that
                                                          subjects (a random sample of either right or left foot
these relationships would not be present in those
                                                          measurements was used) for forefoot angle, relaxed
subjects with a near neutral forefoot alignment.
                                                          rearfoot angle, and navicular drop.
METHODS                                                      A gait template was constructed for each subject to
                                                          ensure that the same foot placement angle was used
   Fifty-one subjects volunteered for this study: 26      for all standing measures. Each subject was asked to
male and 25 female (mean ± SD age, 34 ± 11.2 years;       walk along a 4-m length at his/her preferred speed
height, 170 ± 9.25 cm; body mass, 73.2 ± 15.7 kg).
                                                          and come to a stop on a 45 × 60-cm piece of paper.
Subjects with a history of congenital deformity, sur-
                                                          Subjects were asked to end their walk in bilateral
gery, or traumatic injury to either lower extremity in
                                                          stance with both lower limbs in a foot placement
the previous 6 months were excluded. This study was
                                                          angle that was most comfortable to them. Four
approved by the Internal Review Board at the Univer-
sity of Virginia and all subjects provided informed       practice trials were allowed and on the fifth trial each
written consent.                                          foot was traced with a ballpoint pen. The foot
   Static foot measurements, including forefoot angle,    placement angle was recorded as the angle from the
subtalar joint neutral rearfoot angle, relaxed rearfoot   line of forward progression to a line that bisected the
angle, and navicular drop, were taken by the primary      foot from the mid heel through the second toe.
investigator, who had over 6 years of experience             With the subject lying prone, with 1 leg extended
making these measurements. All measurements were          and the other leg externally rotated and bent at the
recorded by an assistant. All measurements were           knee at approximately 90°, the heel and lower leg
taken 3 times and an average was calculated. On 19        were marked for rearfoot measurements (Figure 1).
subjects the anatomical landmarks were erased after       A line was drawn on the extended leg bisecting the
first set of measurements with an alcohol swab. The       lower one third of the leg and another line was
subject walked around the clinic for approximately        drawn bisecting the calcaneus.8 Subtalar joint neutral

560                                                   J Orthop Sports Phys Ther • Volume 35 • Number 9 • September 2005
was then determined using the palpation method.22
With the subtalar joint held in neutral, the fourth
and fifth metatarsal were loaded, bringing the ankle
in dorsiflexion until firm resistance was felt6,14 (Fig-
ure 2). Subtalar joint neutral position in non-weight
bearing was used as a reference position for forefoot
measurements. While one hand held the subtalar
joint in its neutral position, the opposite hand was
used to align a goniometer for the forefoot measure-
ment. Forefoot position was determined by placing
the stationary arm of the goniometer at 90° to the
bisection of the calcaneus and aligning the moveable
arm along a plane that would bisect the metatarsal
heads (Figure 3). Forefoot varus (positive degrees),
neutral (0°), or valgus (negative degrees) was deter-
mined as the angle between the perpendicular to the
bisection of the calcaneus and an imaginary line
drawn through the metatarsal heads.18

                                                                 FIGURE 4. Positioning for relaxed standing rearfoot angle measure-
                                                                 ment.




                                                                                                                                      RESEARCH
                                                                    Then, each subject stood on a 22.5-cm–high box
                                                                 with the subject’s feet positioned in his/her gait
                                                                 template.15 The rearfoot angle was assessed in both
                                                                 the subtalar joint neutral and relaxed standing posi-
                                                                 tion. To assess rearfoot angle in subtalar joint neutral,
                                                                 each subject was placed in his/her gait template and
                                                                 subtalar joint in neutral was palpated. With the
                                                                 subtalar joint positioned in neutral, the rearfoot




                                                                                                                                      REPORT
                                                                 angle was measured as the angle between the bisec-
                                                                 tion of the lower one third of the leg and the
                                                                 bisection of the calcaneus.6 The relaxed rearfoot
                                                                 angle was then measured using the same landmarks
                                                                 and gait template, with the subject in single-leg
                                                                 relaxed stance16 (Figure 4). For this measurement,
                                                                 the subject flexed the opposite knee and was allowed
                                                                 to touch that toe to the surface and hold onto a
FIGURE 2. Positioning for forefoot angle measurement with the
                                                                 metal bar for balance, if necessary.
subtalar joint in a neutral position (left foot).                   Navicular drop measurements were completed as
                                                                 per others in the literature.1,9,12,19,23,29 Navicular
                                                                 height was measured in subtalar joint neutral and
                                                                 relaxed stance. The navicular bone of each foot was
                                                                 palpated and a mark was made with a ballpoint pen
                                                                 on the most prominent aspect. The subject then
                                                                 stood in his/her gait template, on the box, in
                                                                 bilateral stance, and the subtalar joint in neutral
                                                                 position was palpated. An index card was placed
                                                                 vertically along the medial aspect of the foot and a
                                                                 mark was made on the card at the level of each
                                                                 marked navicular.2,23 Each subject then lifted 1 foot
                                                                 off the box, bending the knee, and the navicular was
                                                                 marked on the index card during relaxed unilateral
                                                                 stance. This was repeated for the opposite foot. The
                                                                 difference in navicular height measured during bilat-
                                                                 eral and unilateral stance was defined as navicular
FIGURE 3. Goniometric forefoot angle measurement (right foot).   drop2,23 (Figure 5).

J Orthop Sports Phys Ther • Volume 35 • Number 9 • September 2005                                                              561
                                                                           performed on the low (n = 8) and high (n = 5)
                                                                           subgroups because of an insufficient number of
                                                                           subjects in these groups.

                                                                           RESULTS
                                                                              ICC3,3 for reliability was 0.97 for the measurement
                                                                           of forefoot angle, 0.90 for relaxed rearfoot angle, and
                                                                           0.96 for navicular drop, based on a random sample of
                                                                           the left or right foot for 19 subjects. In the sample (n
                                                                           = 51), the mean (±SD) forefoot position was 4.4°
                                                                           (±3.4°) (Table 1). Using the subgroup classification
                                                                           for forefoot angle, 38 cases were considered neutral
                                                                           (75%), 5 cases were considered high forefoot varus
                                                                           (10%), and 8 cases were considered low forefoot
                                                                           varus (some being valgus, but not all) (15%) (Table
                                                                           2).
                                                                              The level of association between forefoot angle and
                                                                           rearfoot angle in relaxed stance in the aggregate data
                                                                           (n = 51) was r = 0.52 (P .001). When the data were
FIGURE 5. Positioning for navicular drop measurement.                      subdivided based on forefoot angle, there was no
   The relationships between forefoot angle and                            significant relationship noted in the neutral forefoot
weight-bearing midfoot position (navicular drop),                          subgroup (1.0° forefoot angle 8.0°) (r = 0.19, P =
also between forefoot angle and relaxed rearfoot                           .24) (Figure 6).
angle in stance, were determined using the Pearson                            The level of association between forefoot angle and
product moment coefficient (r).18 For reasons of                           navicular drop in the aggregate data was r = 0.55
comparison to other research, correlations between                         (P .001). There was no relationship noted between
forefoot angle and rearfoot angle in subtalar joint                        forefoot angle and navicular drop in the neutral
neutral, and between relaxed rearfoot angle and                            forefoot (1.0° forefoot angle 8.0°) subgroup (r =
navicular drop, were calculated.                                           0.01, P = .96) (Figure 7).
   Data were collected on 51 subjects. Initial sampling                       The level of association between relaxed rearfoot
included both feet for a count of 102 feet. Due to the                     angle and navicular drop was r = 0.43 (P = .002).
strong association between the right and left foot for                     When the data were subdivided based on forefoot
each person, a random sample of either left or right                       angle, there was no significant relationship between
foot was chosen for correlational analyses for a total                     relaxed rearfoot angle and navicular drop in the
of 51.17,21 Correlations were examined in the whole                        neutral subgroup (r = 0.32, P = .055). The overall
group (n = 51) to investigate the relationship of the 3                    correlation between forefoot angle and rearfoot
measures. Based on the forefoot mean and 1 stan-                           angle in subtalar joint neutral was not significant (r =
dard deviation of the data (n = 51), subjects were                         0.17, P = .24).
subsequently divided into 3 subgroups, based on
degree of forefoot angle. Subjects whose forefoot                          DISCUSSION
angle fell between 1.0° and 8.0° were considered to
have a ‘‘neutral,’’ those whose forefoot angle was                           The purpose of this study was to investigate the
greater or equal to 8.0° were considered to have a                         relationships between forefoot angle and relaxed
‘‘high,’’ and those whose forefoot angle was less than                     rearfoot angle, and between forefoot angle and
or equal to 1.0° were considered to have a ‘‘low’’                         navicular drop, in a healthy population. Measures of
forefoot varus angle. Then, correlations were exam-                        forefoot angle, relaxed rearfoot angle, and navicular
ined in the neutral subgroup (n = 38) for all 3                            drop were found to be reliable (ICC 0.90). All
measures; however, correlational analyses were not                         measures were taken by a primary investigator and

 TABLE 1. Descriptive statistics for a random sample of left or right feet (n = 51).
                                     Minimum           Maximum             Range        Mean          SEM            SD
 Forefoot angle (°)                    –4.5              13.7              18.2          4.4          .48            3.4
 Relaxed rearfoot angle (°)             3.0              16.0              13.0         10.5          .37            2.7
 Navicular drop (mm)                   –2.6              17.0              19.6          6.2          .63            4.5
 Abbreviations: SEM, standard error of the mean; SD, standard deviation.


562                                                                  J Orthop Sports Phys Ther • Volume 35 • Number 9 • September 2005
 TABLE 2. Descriptive statistics for subgroups based on mean ±1 standard deviation of forefoot angle values.
          Forefoot Angle
          Subgroups/Foot
           Measurement               N              Minimum         Maximum       Range       Mean         SEM         SD
 High ( 8° varus)
   Forefoot angle (°)                 5              8.0            13.7           5.7        10.4         1.1         2.5
   Relaxed rearfoot angle (°)         5              6.7            15.3           8.6        11.2         1.7         3.8
   Navicular drop (mm)                5             10.8            17.0           6.2        13.2         1.1         2.4
 Neutral (1.0°-8.0° varus)
   Forefoot angle (°)                38              1.3             7.7           6.4         4.8         0.3         1.7
   Relaxed rearfoot angle (°)        38              5.3            16.0          10.7        11.0         0.3         2.1
   Navicular drop (mm)               38             –1.2            13.3          14.5         6.1         0.6         3.7
 Low ( 1.0° varus)
   Forefoot angle (°)                 8             –4.5             1.0           5.5        –0.9         0.8         2.1
   Relaxed rearfoot angle (°)         8              3.0            10.6           7.6         7.4         1.0         2.7
   Navicular drop (mm)                8             –2.6             8.0          10.6         2.0         1.2         3.5
 Abbreviations: SEM, standard error of the mean; SD, standard deviation.


recorded by an assistant; however, it should be noted                      may be due to variations in measurement technique,
that while the primary investigator did not record the                     especially in the amount of force placed through the
actual linear value, there might have been uninten-                        fourth and fifth metatarsal heads when loading the
tional potential to recall general visual estimates. All                   forefoot. There are potential reliability issues when
of the intrarater reliability scores were considered                       using foot measurement techniques in the non–




                                                                                                                                        RESEARCH
excellent and in accordance with other authors.3,8,10                      weight-bearing position. While good test-retest reli-
While measurements of subtalar joint neutral in                            ability was demonstrated in this study (ICC3,3 = 0.95)
non-weight bearing have not been found to be                               and in the study by Donatelli et al6 (ICC = 0.99),
reliable, measurements in weight bearing have been                         other authors have questioned the reliability of non–
found to have good intrarater reliability.7,27 Intrarater                  weight-bearing measurements.19 Due to these differ-
reliability has been proven to be better when the                          ences, we believe it is important to establish one’s
investigator is experienced and when more than 2                           own reliability, as well as sample mean and standard
measures are taken for each position.25 Both strate-




                                                                                                                                        REPORT
                                                                           deviation, for these measures. Establishing good reli-
gies were used in our study.                                               ability of both the dependent and independent
   We collected forefoot, rearfoot, and navicular drop                     variables also helps to strengthen the internal validity
measurements on 51 individuals, sampling both feet                         of the study. Based on the measures from the
for an initial count of 102 feet. In this study, to                        investigator of this study, 1.0° to 8.0° of forefoot varus
respect the assumption of independence, only data                          was considered neutral, as defined by the mean ±
from 1 foot (randomly selected for each subject)                           standard deviation. Our average navicular drop meas-
were used. Menz17 reported that there is a potential                       ure (mean, 6.2 mm) was in accordance with others
for data inflation when using measurements from the                        who have reported averages ranging from 6.1 to 7.58
right and left foot of the same individual. He                             mm.4,18,23 Finally, our average rearfoot angle in
therefore advocated either averaging the left and                          single-limb stance (10.5° ± 2.7°) also fell within the
right foot data, or randomly selecting either the right                    ranges found by others (6.2° ± 3.9° to 12.2° ±
or left foot for analysis.17 The drawback in averaging                     4.0°).4,18,28 Given the good reliability of the measures
data from the right and left foot is the potential for                     and general agreement of our values with others in
obscuring valuable information. While there is a                           the literature, we felt confident in studying relation-
potential for losing valuable information by randomly                      ships between variables.
selecting either the right or left foot, the benefit is                       The relationship between forefoot angle and re-
that assumption of independence is not violated.17,21                      laxed rearfoot angle in stance is based on the
   In the data studied (n = 51) a forefoot varus angle                     principle that when a forefoot varus angle is present,
was present in 92% and a forefoot valgus angle was                         the rearfoot will evert to bring the foot parallel to the
present in 8% of the cases. The overall high inci-                         ground. It is not known whether forefoot varus leads
dence of forefoot varus angle compared to forefoot                         to midfoot/rearfoot pronation or if midfoot/rearfoot
valgus angle is in agreement with data reported by                         pronation over a long period of time creates a
Donatelli et al,6 who found a forefoot varus frequency                     forefoot varus due to medial loading. Regardless, our
of 90.5%, and by Garbalosa et al,8 who found a                             results suggest that they are related. We noted an
frequency of 87%. However, our results conflict with                       overall correlation between forefoot angle and re-
those of McPoil et al,14 who recorded forefoot varus                       laxed rearfoot angle in stance of r = 0.52 (P .001).
in only 8.95% of their 27 subjects. This discrepancy                       This suggests that 27% of the variance in relaxed

J Orthop Sports Phys Ther • Volume 35 • Number 9 • September 2005                                                                563
FIGURE 6. (A) Relationship between forefoot angle and relaxed           FIGURE 7. (A) Relationship between forefoot angle and navicular
rearfoot angle across all subjects. (B) Relationship between forefoot   drop across all subjects. (B) Relationship between forefoot angle and
angle and relaxed rearfoot angle in the neutral forefoot subgroup.      navicular drop in the neutral forefoot subgroup.

rearfoot angle may be related to forefoot structure.                    the relationship becomes more apparent. This is true
Donatelli et al6 assessed the relationship between                      of most structural deviations. A leg length discrep-
forefoot varus and peak rearfoot angle during the                       ancy of 5 mm may not result in compensatory
stance phase of gait and also found a positive                          biomechanics; however, one of 20 mm is likely to lead
correlation.                                                            to significant adaptations. This may explain, in part,
   Interestingly, there was no relationship between                     the lack of significant findings in previous studies by
forefoot angle and relaxed rearfoot angle in the                        McPoil and Cornwall16 and Mueller et al,18 where the
neutral subgroup (r = 0.19, P = .24). These data                        forefoot angles studied may have been in a narrower
suggest that people with an average amount of                           neutral range of values. One could make the argu-
forefoot varus do not necessarily exhibit the proposed                  ment that if the neutral subgroup had a limited
relationship between forefoot and rearfoot position.                    range of values, it would reduce the strength of the
However, as the structural malalignments increase,                      correlation. However, the range of values in our study

564                                                                J Orthop Sports Phys Ther • Volume 35 • Number 9 • September 2005
in each of the subgroups was similar (high, 5.7°;              over the marked navicular. In our study it is impor-
neutral, 6.4°; low, 5.5°) and sample of 38 subjects in         tant to note that while the navicular was marked in
the neutral subgroup should have provided enough               subtalar joint neutral, it was not remarked again in a
statistical power to see a correlation if there was one.       standing relaxed position. This may have resulted in
The strength of our correlation between forefoot               underestimation of the true excursion of the
angle and relaxed rearfoot position seems to be                navicular drop.
driven by the high and low subgroups data. While we               Midfoot and rearfoot pronation are not always
recognize that we do not have enough subjects in our           correlated. Some individuals have fairly vertical
high and low subgroups to be studied independently,            calcanei during stance in the presence of midfoot
future research investigating foot structure should            pronation. Lundberg et al13 found that during foot
include these extremes.                                        pronation, the largest amount of motion occurred in
   Mueller et al18 assessed the correlation between            the talonavicular joint, followed by the talocalcaneal
forefoot angle and rearfoot angle in subtalar joint            joint. The correlation between relaxed rearfoot angle
neutral position as opposed to relaxed calcaneal               and navicular drop in the entire group of subjects
stance.18 The authors found no correlation between             was r = 0.43 (P = .002), where 19% of the variance
rearfoot and forefoot position (r = 0.00-0.14). This           could be explained between the 2 variables. The
finding would be expected because their measure of             findings of Cornwall and McPoil5 support this rela-
rearfoot angle in subtalar joint neutral did not take          tionship. Their research determined that the
into account possible pronation compensation. When             calcaneus and navicular had interdependent motion
we examined the relationship between forefoot angle            during walking. Further, using a stepwise multiple
and rearfoot angle in the subtalar joint neutral               regression analysis with 17 static measurements en-
position, we also found no significant correlation.
                                                               tered, McPoil et al16 found that navicular drop was
   While assessing the midfoot position with external




                                                                                                                         RESEARCH
                                                               the significant predictor selected in the prediction of
markers is difficult, navicular drop provides an indica-
                                                               maximal rearfoot eversion. Their correlation of r =
tion of midfoot pronation. Therefore, we also sought
                                                               0.42 matched that of Mueller et al,18 who also found
to examine the relationship between forefoot angle
and navicular drop. The correlation between forefoot           a significant correlation of r = 0.42 between rearfoot
angle and navicular drop in the entire group of                angle and navicular drop. Unlike our other findings,
subjects was r = 0.55 (P .001), with 30% of the                the correlation between relaxed rearfoot angle and
variance in navicular drop explained by forefoot               navicular drop were very close to significant in our
                                                               neutral subgroup (r = 0.32, P = .055). This may imply




                                                                                                                         REPORT
angle. Our values were higher than those found by
Mueller et al18 (r = 0.29 and 0.33 for the right and           that the movement between the rearfoot and midfoot
left foot, respectively), who found 8% to 11% of the           may be associated even in feet that exhibit a neutral
variance in navicular drop accounted for by forefoot           structural alignment.
angle. The discrepancy in the amount of explained                 Clinicians often perform static foot evaluations on
variance between the 2 studies may be due to sample            patients with the underlying assumption that struc-
range as well as measurement technique. In measur-             ture and function are related.16 Very little data exist
ing forefoot angle, Mueller et al’s18 data revealed a          regarding the relationships between static forefoot,
range of forefoot position from –6.0° to 6.0°, while           midfoot, and rearfoot positions. Results of studies
our data ranged from –4.5° to 13.7°. This variation            assessing the relationship between static measure-
may either be due to the amount of pressure placed             ments and function have been variable. Our study
through the fourth and fifth metatarsal heads or it            revealed that there is a moderate relationship be-
may indicate that we included a wider range of foot            tween forefoot angle and associated relaxed rearfoot
structures. Similar to the findings for the relaxed            angle and navicular drop in a healthy sample. This
rearfoot angle, there was a lack of a relationship             relationship is absent in the neutral range of values,
between forefoot angle and navicular drop in the               which implies that the significance of the correlation
neutral subgroup (r = 0.01, P = .96). This supports            is derived from the high and low extremes of forefoot
our previous suggestion that when forefoot alignment           values. Therefore, the relationship between structure
is within a neutral range, there may not be a need to          and function becomes most evident when considering
compensate through the midfoot or rearfoot.                    foot positions that depart substantially from the
   Individuals may compensate in different ways for            mean. Again, it should be noted that our data were
structural positions or malalignments. For example, if         based on healthy subjects. It is unknown if foot
rearfoot motion is limited, compensation for forefoot          structure relationships in a population with patholo-
varus may be seen in the midfoot. Midfoot pronation            gies or pain would exhibit the same tendencies. A
is difficult to measure clinically. Navicular drop has         better understanding of forefoot, midfoot, and
been used as a measure of midfoot pronation, or                rearfoot relationships could help clinicians and re-
arch flattening.12,18,24 A possible limitation in using        searchers better refine specific interventions, such as
navicular drop is the potential for skin movement              foot orthotics. Future studies are needed to further

J Orthop Sports Phys Ther • Volume 35 • Number 9 • September 2005                                                  565
investigate the role of forefoot angle on static and                   on controlling abnormal subtalar pronation. Phys Ther.
dynamic measures of the foot in subjects with pathol-                  1994;74:149-158; discussion 158-161.
                                                                 11.   Knutzen KM, Price A. Lower extremity static and
ogy.                                                                   dynamic relationships with rearfoot motion in gait. J Am
                                                                       Podiatr Med Assoc. 1994;84:171-180.
                                                                 12.   Lange B, Chipchase L, Evans A. The effect of low-Dye
CONCLUSIONS                                                            taping on plantar pressures, during gait, in subjects with
                                                                       navicular drop exceeding 10 mm. J Orthop Sports Phys
  Based on the results of this study, we conclude that                 Ther. 2004;34:201-209.
there is a significant relationship between forefoot             13.   Lundberg A, Svensson OK, Nemeth G, Selvik G. The
angle and relaxed rearfoot angle, as well as between                   axis of rotation of the ankle joint. J Bone Joint Surg Br.
forefoot angle and navicular drop in healthy subjects.                 1989;71:94-99.
These relationships were not found when forefoot                 14.   McPoil T, Knecht H, Schuit D. A survey of foot types in
                                                                       normal females between the ages of 18 and 30 years.
varus values were within a standard deviation of the                   J Orthop Sports Phys Ther. 1933;9:406-409.
sample mean.                                                     15.   McPoil TG, Cornwall MW. Relationship between three
                                                                       static angles of the rearfoot and the pattern of rearfoot
                                                                       motion during walking. J Orthop Sports Phys Ther.
ACKNOWLEDGEMENTS                                                       1996;23:370-375.
                                                                 16.   McPoil TG, Cornwall MW. The relationship between
  The authors would like to acknowledge Dr Joe                         static lower extremity measurements and rearfoot mo-
Gieck and Dr Ethan Saliba for their contribution to                    tion during walking. J Orthop Sports Phys Ther.
this study. Many thanks for the use of the facilities in               1996;24:309-314.
                                                                 17.   Menz HB. Two feet, or one person? Problems associ-
the Frank McCue Center at the University of Virginia.                  ated with statistical analysis of paired data in foot and
                                                                       ankle medicine. The Foot. 2004;14:2-5.
                                                                 18.   Mueller MJ, Host JV, Norton BJ. Navicular drop as a
                                                                       composite measure of excessive pronation. J Am Podiatr
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566                                                         J Orthop Sports Phys Ther • Volume 35 • Number 9 • September 2005