Lateral wedges - a crossover study
BACKGROUND:
Osteoarthritis (OA), commonly affecting the
knee joint, is one of the most prevalent chronic
musculoskeletal disorders and is a leading
cause of long-term physical disability affecting
adults [1]. While we are unaware of joint specific
indicators of the economic burden of OA, a
recent report indicates that more than 6.9% of
the adult population in the Unites States had
symptomatic knee OA in 2007-2008 [2] – a
number that is expected to rise dramatically in
the coming decades. Further, symptomatic OA
(the combination of symptoms and radiographic
evidence of OA) is more commonly found in the
knee than in any other joint [3]. Given that there
is no cure for knee OA and the overall economic
burden of OA is high, there has been a recent
push towards the identification of non-surgical,
non-pharmacological treatments for knee OA
that can be delivered effectively, safely, and with
minimal personnel and economic resources
[4]. Shoe-worn insoles/orthotics are a low-cost
and low-burden self-management option that
has widespread appeal for managing knee OA
symptoms.
Recent research confirms the link between
knee and foot problems in people with knee OA.
An examination of data from the Osteoarthritis
Initiative showed that 25% of individuals with
painful knee OA concurrently report foot pain,
and that the presence of foot pain adversely
affected overall health and function [5].
Individuals with knee OA also tend to exhibit
more pronated feet compared to those without
knee OA [6, 7]. Indeed, a recent study involving
164 people with symptomatic medial tibiofemoral
OA reported that 45% had pronated or
severely pronated feet [8]. Recent research
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has also shown that the presence of foot/ankle
symptoms significantly increases the odds of
developing knee OA symptoms and symptomatic
radiographic knee OA [9]. Additionally, rearfoot
eversion during walking has also been shown
to be associated with medial compartment knee
joint load, as quantified by the external knee
adduction moment (KAM) [10]. Specifically, more
rearfoot eversion appears to be associated
with lower KAM values. Finally, older adults
with pronated feet are more likely to exhibit
knee pain and medial tibiofemoral cartilage
damage than older adults with other foot
types [11]. Taken together, these findings
indicate that people with pronated feet form
a large, and clinically relevant, sub-group of
the population with knee OA. Thus, targeted
treatment approaches for this subgroup that
considers their unique biomechanical needs
may be warranted. However, current methods
for the treatment of knee OA symptoms and
biomechanics has typically failed to directly
address any aspect of foot biomechanics
in general, and in those with knee OA and
concomitant pronated feet specifically.
A commonly studied conservative treatment
approach for knee OA is shoe-worn insoles, in
particular insoles that are built up along the
lateral edge (lateral wedges). There have been a
number of studies examining the biomechanical
and clinical changes associated with use of
lateral wedges. Although lateral wedges have
been shown to provide immediate reductions
in KAM magnitudes [12, 13] – consistent with
the reported negative correlation between
increased rearfoot eversion (which would occur
with lateral wedging) and the KAM [10] – the
effects on knee symptoms are less clear [14]. A
primary limitation of previous lateral wedges for