Inverted
posture
‘A Rearfoot
good fit?’
variables and compared the differences in
rearfoot posture between knees with and
without PFOA. Subsequently, the values of
calcaneus inverted angle were compared using
analysis of covariance. Covariates included age,
sex, BMI, TF joint K/L grade, corrected AAA,
presence of varus thrust, and knee flexion ROM.
These covariates were chosen based on clinical
judgment and previous studies investigating
factors associated with PFOA or rearfoot
posture [21, 35–37]. The normality of calcaneus
inverted angle was assessed using the Shapiro-
Wilk test and the homogeneity of the variances
between patients with and without PFOA was
confirmed using the F-test.
Age, years 74.69 ± 7.785
Female, no. (%) 51 (75.0)
Body mass index, kg/m2 24.14 ± 3.753
Corrected anatomical axis angle, degrees 176.2 ± 4.951
Presence of varus alignment, no. (%)a 55 (80.9)
Medial tibiofemoral joint K/L grade, no. (%)b
Grade 2 48 (70.6)
Grade 3 11 (16.2)
Grade 4 9 (13.2)
We further performed multiple logistic
regression analyses and calculated odds ratios
(ORs) and their 95% CIs. Logistic regression
analyses were performed first with an
unadjusted model and then with a propensity
adjusted model. Due to the small sample size,
we used propensity score adjustment including
the above covariates. Data analyses were
performed with JMP Pro 12.2 (SAS Institute,
Cary, NC, USA). P-values <0.05 were considered
statistically significant. Presence of varus thrust, no. (%) 12 (17.6)
Results
Figure 2 shows flowchart describing the
inclusion of study participants. One-hundred-
forty-three patients with medial knee OA
were enrolled at baseline period (February
2014). Of these patients, 75 were excluded
from this study; 41 could not be contacted or
declined follow up for non-specific reasons;
and 34 were excluded because of missing
data on patient’s characteristics, radiography,
and rearfoot posture at the 12 months follow
up period (January 2015). Thus, our final
30
Table 1: Patients’ characteristics at follow up period (n = 68)a
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Knee range of motion, degrees
Extensionc −6.471 ± 6.482
Flexion 140.8 ± 12.17
Presence of any PFOA, no. (%) 38 (55.9)
Presence of mixed PFOA, no. (%) 19 (27.9)
Presence of medial PFOA, no. (%) 22 (68.8)
Presence of lateral PFOA, no. (%) 26 (32.4)
Coexisting medial TFOA and any PFOA, no.
(%) 38 (55.9)
Calcaneus inverted angle, degreesd −0.357 ± 5.522
K/L grade: Kellgren/Lawrence grade; PFOA: patellofemoral osteoarthritis;
TFOA: tibiofemoral osteoarthritis
Except where otherwise indicated, values are mean ± SD
a Varus alignment is defined as corrected anatomical axis angle < 179
degrees
b If participants did not get worse their clinical symptoms within the
12-month follow-up period, radiography at baseline was used for K/L grade
assessment
c A negative value indicates that the knee is flexed
d A positive value indicates inversion direction of the calcaneus