|
Townsend's
Patented
Hinge
Movement:
Within
the
first
25
degrees
of
flexion,
the
orthotic
mechanism
moves
8-9mm
posterior
which
simulates
the
normal
roll
and
glide
ratio
of
the
femur
on
the
tibial
plateau.
|
Planes
of
Motion
There
are
two
planes
of
motion
at
the
knee:
The
rotation
of
the
tibia
and
the
femur,
and
flexion
and
extension.
These
can
be
described
as
rolling
and
gliding
movements.
These
planes
of
motion
are
altered
when
an
injury
to
the
knee
occurs.
Rotation
of
the
Tibia
and
Femur
In
flexion,
the
tibia
lies
beneath,
and
in
line
with,
the
midpoint
of
the
patella
(knee
cap).
As
extension
occurs,
the
tibia
externally
rotates
and
the
tibia
tubercle
comes
to
lie
lateral
to
the
midpoint
of
the
patella.
The
extent
of
the
rotary
movement
is
roughly
equivalent
to
half
the
width
of
the
patella.
When
the
knee
is
fully
flexed,
the
tibial
tubercle
points
to
the
inner
half
of
the
patella;
in
the
extended
knee
it
is
in
line
with
the
outer
half.
A
locking
motion
of
the
femur
and
the
tibia
which
occurs
when
the
two
bones
reach
full
extension
is
called
the
"screw
home
mechanism."
The
orbital
shapes
of
the
femoral
condyles
and
maximum
contact
of
the
large
bony
surfaces
creates
this
locked
position
of
the
knee.
Rolling
and
Gliding
during
Flexion
and
Extension
The
movement
of
the
femur
relative
to
the
tibia
during
flexion
and
extension
follows
a
rolling
and
gliding
pattern.
Theoretically,
if
a
pure
rolling
motion
was
involved,
the
femur
would
roll
off
the
tibial
plateau.
Likewise,
if
a
purely
gliding
motion
was
involved,
the
femur
would
engage
the
posterior
rim
of
the
tibial
plateau.
The
movement
of
the
femur
relative
to
the
tibia
generated
by
a
combination
of
rolling
and
gliding,
represents
the
true
physiologic
action
of
the
tibiofemoral
joint.
Motion
of
the
Townsend
Patented
Hinge
One
of
the
primary
features
of
Townsend's
custom
and
pre-sized
knee
braces,
and
orthotic
componentry,
is
our
patented
hinge.
This
joint,
which
is
exclusive
to
Townsend
braces,
more
closely
replicates
the
natural
motion
of
the
knee
than
any
of
our
competitor's
products.
The
Townsend
hinge
counters
tibial
shear
with
an
8-9mm
posterior
tibial
movement
during
the
first
25
degrees
of
knee
flexion.
This
roll
and
glide
motion
matches
the
arthrokinematics
of
a
normal
knee,
allowing
the
orthotic
joint
to
act
as
an
external
guide
to
maintain
the
normal
anterior/posterior
positional
relationship
of
the
femur
and
tibia
through
the
entire
range
of
motion. |
