Inverted
posture
‘A Rearfoot
good fit?’
al. found that patients with PF pain exhibited
increased rearfoot inversion compared to
those without PF pain in younger adults when
examined using a goniometer [20]. The presence
of both PF pain and altered foot posture can
lead to this progression given that PF pain in
younger adults is suggested to be a precursor
to PFOA. However, due to the cross-sectional
nature of this study, PFOA may develop first and
altered rearfoot posture may be a consequence
of PFOA. Bidirectional segmental relationship
has been determined among foot, shank, thigh,
and pelvis [40]; therefore, a prospective cohort
study on the incidence of PFOA in patients with
inverted rearfoot but without PFOA should be
conducted. This is particularly important given
that risk factors associated with the incidence
and progression of PFOA have not been fully
determined.
It should be noted that there was a large
interindividual variability of calcaneus inverted
angles, although patients with coexisting PFOA
had an inverted calcaneus 3.1° greater than
those with isolated medial TFOA. Understanding
these variabilities is important because
interventions concerning foot orthoses targeting
PF joint disease may lack clinical significance
[19, 41] and evaluating individual rearfoot
posture may facilitate pain reduction of foot
orthoses. Sultive et al. found that increased
inverted calcaneus during standing is a potential
indicator of non-success in the treatment of foot
orthoses for improving PF pain [42], indicating
a substantial role for rearfoot posture on foot
orthoses in targeting the PF joint.
The current study included patients with
medial TFOA and compared rearfoot posture
in patients with and without PFOA because
mixed OA is common [5–7] and is likely to be
more painful than those with isolated PFOA
[43]. However, the observed relationship
between varus thrust and the presence of PFOA
in patients with medial knee OA may not be
true for patients with isolated PFOA that was
suggested as a precursor of mixed OA [44].
There are some limitations to be noted. First,
the cross-sectional study design limits our ability
to identify causality between inverted rearfoot
posture and PFOA. Second, a foot scanning
system was used for static measurements
while standing. Evaluating dynamic rearfoot
alignment through three-dimensional motion
capture apparatus [45] may provide substantial
information about the association between foot
posture and PFOA with higher accuracy and
reliability than static measure [46]. Furthermore,
calcaneus inverted angle does not include the
subtalar joint and may yield different values
compared to traditional evaluation methods
that use goniometers for evaluating rearfoot
posture [47]. Nevertheless, this scanning system
is advantageous because it has a high accuracy
for measuring static foot posture [29] which can
be clinically assessed in a short amount of time.
Third, PFOA identification using radiographs
is an important limitation. Radiographic
assessment indirectly measures the cartilage
and is less sensitive than MRI. This would lead to
differences in the prevalence of coexisting PFOA.
Specifically, patients with isolated TFOA may
have cartilage damage in the PF joint without
radiographic evidence of PFOA. Furthermore,
radiographic views might be affected by knee
position and the patellar alignment. Fourth, this
study included subjects who did not undergo
follow-up x-ray is an important limitation. Some
of the individuals who did not have PFOA at
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