On Your Nerves… The Basics of Foot-Related Nerve Injuries
By Perry H. Julian, D.P.M.
Anyone who has experienced foot pain during
fitness activities knows how much it can affect technique and
performance. Foot pain can be caused by injuries to bones, ligaments,
tendons, muscle, and other soft-tissue structures. It is also
possible to injure one or more of the nerves that provide sensations
to the foot.
When a nerve is injured, it usually results in paresthesia, which
is an alteration in sensation, and may feel like pins and needles,
numbness, or a sharp or burning pain. Very often, eliminating
the cause of the irritation resolves these problems; however,
if the irritation is left untreated, more serious problems can
develop. The areas of the foot where active people most commonly
experience these nerve problems are the toes, the inside of the
ankle, and the top of the foot.
MORTON'S NEUROMA
A neuroma is the thickening of a nerve that
usually occurs from chronic irritation caused by tight-fitting
shoes or socks, repeated pressure on the ball of the foot, or
abnormal foot biomechanics such as overpronation that can result
in injury to the nerve or its surrounding structures.
The most common location for a neuroma on the foot is between
the third and fourth metatarsals and toes. Known as a Morton's
neuroma, this condition usually has symptoms that include a burning
or tingling sensation in the ball of the foot that radiates out
to the third and fourth toes. You may also experience a cramping
of the toes or a sensation that your socks are bunching up underneath
your feet. If you remove your shoes and massage the area, these
sensations will decrease, but the pain and discomfort usually
recur when you resume activity.
Treatment for a Morton's neuroma involves removing the pressure
that is causing the nerve irritation and reducing the inflammation
around the nerve. Often, if you switch to an athletic or dress
shoe with a wider toe box, the symptoms decrease or even disappear.
Using a toe separator between the affected toes may also take
pressure off the nerve.
If this self-care treatment does not relieve the discomfort, injection
therapy can often reduce the inflammation around the nerve. If
abnormal foot biomechanics are contributing to the problem, orthotics,
combined with a metatarsal pad or other modifications to spread
the metatarsals from each other, take pressure off the nerve.
In most cases, conservative care will alleviate the problem. However,
in resistant cases, it may be necessary to surgically remove the
inflamed nerve branch to provide relief. This treatment will usually
result in complete resolution of the problem.
TARSAL TUNNEL SYNDROME
People who use computer keyboards a lot
are well aware of an injury in the hand and wrist known as carpal
tunnel syndrome. A similar problem, tarsal tunnel syndrome, can
occur in the foot. The tarsal tunnel is an area on the side of
the ankle through which the posterior tibial nerve passes to enter
the foot. This nerve branches off to supply sensation to the inside
of the ankle and the bottom of the foot. If the tarsal tunnel
becomes inflamed, it can constrict the nerve and cause the following:
a burning pain along the inside of the ankle; a sharp, shooting
pain that goes up or down the leg or foot known as Tinel's sign;
and even numbness along the bottom of the foot and heel. These
symptoms can sometimes be confused with the pain of heel spur
syndrome.
Tarsal tunnel syndrome can be caused by a direct or indirect injury
to the nerve. It can also result from abnormal lower extremity
biomechanics.
Once diagnosed, initial treatment for tarsal tunnel syndrome may
include oral or injectable antiflammatory medication. Your doctor
may also prescribe orthotics to control any abnormal foot or ankle
motion that may be contributing to the problem. If the pain persists,
your doctor may recommend a surgical procedure to release the
structures impinging on the nerve. However, in many cases conservation
care can resolve this problem if you treat it early.
FOOT NUMBNESS
Pain or numbness on the top (dorsum) of
the foot is another common complaint of fitness-oriented people.
Coursing along the top of the foot, very close to the skin, are
small nerve branches that supply sensation to the top of the foot
and toes. Because these nerves are so superficial, they are prone
to irritation.
These nerves are usually injured by a shoe laced too tightly across
the top of the foot or by prominent bones or bone spurs that cause
irritation. The pressure from this irritation may lead to a pins
and needles sensation or burning across the top of the foot. If
left untreated, this irritation can progress to complete numbness
in parts of the foot.
Initial treatment for this problem consists of loosening or altering
the pattern of lacing your shoes to take pressure off the irritated
areas on the top of the foot. You can also use moleskin or adhesive
foam to pad any prominent bone spurs. Larger bone spurs may need
to be removed surgically. However, if these bone spurs are the
result of abnormal foot biomechanics, you can use an orthotic
to slow the development of these prominences and in some cases
eliminate the irritation to the affected nerve(s).
Many of these nerve injuries to the foot and ankle are due in
part to temporary stresses that irritate the nerve. These problems
can often be treated conservatively without an loss of training
time. However, numbness, burning, and paresthesias can signify
more involved problems, and you should be evaluated by a sports
medicine physician if these symptoms persist.
Perry H. Julien is a podiatrist and a
Fellow of the American Academy of Podiatric Sports Medicine. This
article is from his book Sure Footing. Copies are available by
sending $11 to The Atlanta Foot and Ankle Center, 5600 Roswell
Rd., Suite 360 North, Atlanta, GA 30342
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