What is Equinus?
One of the most overlooked problems
affecting the lower extremity is a condition known as "Equinus".
The term "Equinus" is derived from
the word "equus", Latin for "horse". It is also
where we get the word "equestrian".
In this case, the term refers specifically to
the horse's foot.
As you can see in
the picture on the right, horses bear weight not with their heel bones,
or even with the ball of the foot. Rather, horses actually bear
weight on the tips of their toes. Note in the cross section of the
horse's foot on the right that that only the three toe bones are even
visible, and the weight is being borne on the tip of the last toe bone.
A horse's foot
Note that the entire weight-bearing portion of the foot
consists of the three toe bones,
with the weight being born on the tip of the last toe bone.
A horse, then, is permanently in pretty much
the same position as a ballerina when she's in the "en pointe"
position--when she stands on the very tips of her toes.
In fact, the term "Equinus" is used in humans
to describe the same sort of condition when it occurs
pathologically--where the foot exists in an
abnormally "plantarflexed" position, (with the foot bent
downward at the ankle) position.
The foot pictured to the right exhibits a
rather severe equinus deformity. This patient would not even
be able to get the heel bone anywhere near the ground to bear weight.
Besides being used to describe a foot where
the foot is rigidly plantarflexed, structural
equinus"), podiatrists also use the
term in another way.
Equinus position of the foot
Podiatrists also use the term
"Equinus" to refer to the condition where the foot may look
normal, (not being in a plantarflexed position), but when it simply has a diminished ability
to bend up at the ankle--a motion called "dorsiflexion".
The normal foot usually has at least 10
degrees of dorsiflexion past being perpendicular to the leg, as
indicated in the diagram to the left.
a non-Equinus foot-type
To the left we see a foot that is
able to dorsiflex, or bend back at the ankle, at least 10
This would be considered normal range of
motion, and a normal foot insofar as equinus is
If a patient cannot bend the foot up as much
as he should, however, he may be thought of as though he functioned with an
equinus foot. So this condition is sometimes known as a "functional
To the right, however, we see a foot that is not
able to dorsiflex 10 degrees. In fact, this foot is unable to bend
upwards at all, remaining perpendicular to the leg.
While clearly not a "structural" equinus with the foot being
held rigidly in a plantarflexed position like the horse's foot, the
ballerina's "en pointe" position, or the "severe
equinus" picture above, the foot's inability to bend
up at the ankle makes this a good example of a "functional
|Patients with a functional equinus have
particular difficulty when the body weight is transferred forward
through the gait cycle. This is when the foot really needs to be
able to dorsiflex at the ankle.
Why does the foot get positioned in this way
There are two ways this may happen. The first
way is when the bones of the foot are fixed in such a way that the
foot is unable to bend upwards adequately at the ankle.
second way an equinus deformity may be seen is when it is the soft tissues
(muscle, tendon, ligament, e.g.) that prevent the ankle from bending
What kinds of problems does Equinus cause?
Equinus can cause all sorts of problems for the
patient. As a patient transfers his weight forward, It can cause a strain
or tear in the tight Achilles tendon, creating Achilles
tendinitis or Achilles tendon ruptures, it can
change the normal biomechanics of the foot, causing the foot to pronate
strain (fasciitis), bunion
and a host of other problems may result.
In fact, so important is it to recognize equinus
that ignoring this condition can make it immensely difficult to treat any of the
above foot disorders.
What Causes Equinus?
Equinus can be caused by several possible
reasons. Several of the most common causes are:
- Poor shoe choices:
Chronic use of high heel shoes
can create equinus as the muscles in the back of the leg
contract to adapt to the abnormal position the shoes
create. Women who have worn high heel shoes for years
will often have feet that cannot even feel comfortable in
anything other than a 1", 2", or even 3" heel
A weak muscle group on the front of the leg may
be overpowered by the large muscles on the back of the leg.
A neurological condition may cause the posterior muscle group (the back of
the calf) to overpower the muscles
on the front of the leg, pulling the foot into equinus over time.
Patients who have had severe muscle damage to the back of the calf,
substantial scar tissue, an Achilles tendon rupture, or any of a host of
other trauma, will tend to develop equinus because the tendon has healed
tighter in a scarred-down position.
"Iatrogenic" means that the condition
is caused by the doctor. An example of a doctor creating equinus
is when the patient is casted in an plantarflexed position. This is
common, for example, when we try to cast the foot in this way to decrease
the pull on the Achilles tendon while it heals from an injury.
Excessive scar tissue following surgery on the Achilles tendon is another
example of an iatrogenic cause of equinus.
Sometimes the muscles on the back of the leg may
be too short or contracted from the position in the womb.
A bony blockage may be preventing the ankle from
bending upwards, resulting in what's known as a 'bony equinus'.
Arthritis, trauma, tumours, and fractures are examples of some of the more
common reasons abnormal bone formation will form to create equinus.
How Do You Treat Equinus?
In most cases, equinus may be treated by proper
stretching. Muscle strengthening of the anterior leg muscle group or
addressing any neurological factor contributing to the condition may be
indicated. Surgery may be indicated to lengthen contracted soft tissue,
or, in cases where a bone is blocking movement of the ankle joint, surgical
intervention may resolve the bony blockage creating the equinus.