Inverted
posture
‘A Rearfoot
good fit?’
rearfoot posture in patients with coexisting
PFOA may assist clinicians to better understand
the effect of rearfoot posture on PF pathology
and may add to the limited evidence of studies
with PFOA population. Thus, this study aimed
to examine whether altered static rearfoot
posture is associated with higher prevalence
of radiographic PFOA in patients with medial
TFOA in a compartment-specific manner. Such
a relationship would indicate the existence of
a biomechanical association, necessitating a
prospective cohort study to find modifiable risk
factors for the incidence and progression of
PFOA.
Methods
Participants
Participants of this exploratory study were
recruited from the 12-month follow-up period
of a prospective cohort of subjects described
in a previous study, which investigated the
clinical impact of coexisting PFOA in patients
with medial TFOA [21]. Briefly, 143 patients
with medial knee OA were recruited from
a community orthopedic clinic in February
2014 and were followed up for 12 months. The
patients, diagnosed by their attending physician,
were recruited through advertisements and
followed up for 12 months. The inclusion criteria
were (i) age≥50 years; (ii) radiographic OA
(i.e. Kellgren/Lawrence [K/L] [22] grade≥2)
primarily in the medial TF compartment in
one or both knees, as evaluated by weight-
bearing anteroposterior radiographs; and
(iii) the ability to walk independently on a
flat surface without any ambulatory assistive
device. Subjects at baseline were included if
they had medial TFOA, regardless of PFOA
status. No restriction was imposed on laterality;
both patients with bilateral and unilateral
radiographic knee OA were included in this
study. The exclusion criteria were: (i) a history
of knee surgery, (ii) inflammatory arthritis, (iii)
periarticular fracture, (iv) current neurological
problems, or (v) lateral TFOA. Lateral TFOA
was defined as a knee having a K/L grade≥1
along with joint space narrowing (JSN) >0 in
the lateral compartment with JSN=0 in the
medial compartment [23]. In other words, only
patients who had a more severe radiographic
disease in the medial compartment compared
to the lateral compartment (i.e., isolated medial
TFOA or mixed medial and lateral TFOA) were
included in this study. Since medial and lateral
knee OA have distinct characteristics [24], and
most knee OA is the medial type in Japan [25,
26], lateral TFOA (i.e., lateral OA severity >
medial OA severity) was excluded in this study.
The Ethical Committee of Kyoto University
approved this study (approval number: E1923).
Written informed consent was obtained from all
participants at baseline and at 12 months follow-
up.
Radiographic PF joint disease severity
The radiographic data of the lateral and
skyline views at baseline were obtained
from all participants. If clinical symptoms
worsened within the 12-month follow-up period,
participants underwent repeat radiography.
Detailed methods of radiographic evaluation of
disease severity in the PF joints were described
elsewhere [21]. Briefly, a single trained examiner
(HI) assessed radiographic severity for the PF
joint using the K/L grading system adapted to
the lateral and medial facets of the PF joint.
Presence of PFOA was defined as knee with
K/L grade 2 in skyline view or osteophytes 1
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