what-when-how
In Depth Tutorials and Information
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local to a specific site on the foot, for example the metatarsal head) may
be facilitated using a low-friction top cover on the orthosis. This may not
need to be used across the entire orthosis surface, however, otherwise
the heel and arch may slide within the orthosis in the early stages of
stance, and the foot may adversely push against the sides or end of the
shoe, increasing risk of injury at these sites. Reducing shear forces is
complex and has yet to be properly resolved, and 'twin skin' hosiery
(comprising two fine layers of cotton) perhaps offers the best solution at
present.
Foot orthoses for medial compartment
osteoarthritis of the knee
An increasingly popular strategy for managing pain associated with oste-
oarthritis in the medial compartment of the knee is the use of a lateral
wedge under the foot. The desired biomechanical effect is to increase the
eversion moments at the foot with the explicit intention that this will also
increase the valgus moments at the knee (frontal plane moments). The
net effect is a reduction in the varus moment acting at the knee, reduced
varus angulation of the knee and redistribution of load from the medial to
the lateral compartment of the knee. This is associated with reduced knee
pain and it is postulated that even disease progression may be affected.
Some question the logic of deliberately pronating the foot, which may
increase the risk of other forms of foot or lower limb problems, however,
patients being treated in this way already have significant pain and often
reduced mobility, and it is better to focus on these real symptoms and
problems rather than on supposed problems that in fact may never mani-
fest. Many patients who may benefit are on a well defined path towards
knee replacement surgery, so there are very strong clinical and economic
reasons for trying this orthotic strategy first. There are also few reports of
complications from users, which perhaps says a lot about the role of
pronation in causing foot problems. Finally, the most effective way to
reduce the varus moment at the knee using this orthosis is to actually
prevent the foot from pronating while at the same time applying a lateral
wedge to the foot; thus, the foot does not necessarily pronate more than
it otherwise would. Doing this means that the foot is unable to move in
response to the increase in foot eversion moments created by the wedge,
and, in principle, this should increase the expected biomechanical effect
at the knee. The lateral wedge can be placed on the underside of the
orthosis and must run from the heel to the fifth metatarsal head area. It
can cover either the full width of the foot or only about half the plantar
width. It is best suited to those patients with laced and lat or low-heeled
