Neurology is the study of nerves, and
this web page should give you an overview of the subject of the nerves that
relate to the foot and lower extremity. We will divide this discussion
on nerves into their anatomical locations--beginning with the brain and moving
Communication Between The
Brain & The Feet
The brain and the feet
communicate through nerve signals. The brain sends signals down to the
foot and leg to tell them to carry out an action, and the foot sends sensory
signals up to the brain to give the brain information about what they are
experiencing. The signals are transmitted through the spine by what are
known as Spinal Tracts.
Listed below are the major families of spinal tracts:
The major pathways extending from
the foot to the brain (the afferent nerves):
This tract sends sensory signals to
the portion of the brain that is conscious. Light touch (like when
someone touches your big toe with a cotton ball) and tickling sensations are
sent up in the Anterior Spinothalamic
Tract, located on the front of the
spine. Normal touch and positional sensation is sent via the Posterior
Spinothalamic Tract, located on the
back of the spine. Pain and temperature are sent to the brain via the Lateral
Spinothalamic Tract, located on each
side of the spine.
This tract sends signals from the
feet to the cerebellum in the lower back of the skull to give input with
regards to balance (which the cerebellum controls unconsciously).
The major pathways extending from the
brain to the foot (the efferent nerves):
known as the Pyramidal Tract because it starts from a pyramid-shaped area of
the medulla in the brain, this
tract carries signals from the cortex of the brain to the muscles of the
extremities. If you wiggle your toes, you are using this tract.
tract consists of those structures involving involuntary, unconscious or
automatic movement of the skeletal system. If you unconsciously adjust your
position while standing, for example, you are using this tract.
This tract predominately carries
autonomic function (the signals carried without your thinking about them,
such as perspiration and whether to open or close the arteries) down to the
The Nerves of the
Nerves of the Thigh
The nerves of the foot
are all branches of one of two nerves--the Femoral
Nerve, which provides only a small
amount of innervation (nerve supply) to the foot), and the
Nerve, which provides the vast
majority of the innervation to the foot.
Nerve (pictured on the right)
arises from nerve fibers from the the L2-L3-L4 portion of the lumbar
spine. (This means that the nerves leave the spinal cord beneath
the 2nd, 3rd and 4th Lumbar vertebrae.) The Femoral Nerve then
passes down the inside edge of the thigh, past the inside of the knee
and towards the ankle and foot.
Nerve (pictured below) is the largest
nerve in the body and it is comprised of nerves from the L4-L5-S1-S2-S3
level of the spine. (This means that the nerve fibers that make up
the Sciatic Nerve leave the spinal cord beneath the fourth and fifth
lumbar and the first, second and third sacral vertebrae.) It then
descends down the back of the thigh.
You can learn about the most
common injury to the sciatic nerve by visiting our webpage on
sciatic nerve passes down the back of the thigh, and near the bottom third of the
thigh, it branches into two nerves:
Peroneal Nerve, comprised
of nerve fibers from L5, S1, S2, and S3.
comprised of nerve fibers from L4, L5, S1, S2 and S3)
Each of these nerves then continues
down the leg towards the knee joint.
Nerves Below the Knee and
Above the Ankle
Shortly after crossing the
knee joint, the Common Peroneal Nerve
divides into three branches--the
Lateral Sural Cutaneous Nerve, the
Deep Peroneal Nerve and the
Superficial Peroneal Nerve.
Sural Cutaneous Nerve merges with the
Medial Sural Cutaneous Nerve (a branch from the Tibial Nerve described
below) to form the Sural Nerve.
The Sural Nerve then runs down the outside edge of the leg.
Peroneal Nerve begins at the outside
edge of the upper leg, then moves across the tibia bone in the leg to supply
nerve function to the muscles on the front of the leg (the Tibialis
Hallucis Longus, Extensor
Digitorum Longus and Peroneus
Tertius muscles). The Deep
Peroneal Nerve then continues down the leg towards the foot.
Peroneal Nerve supplies nervous
function to the Peroneus Longus and Peroneus Brevis muscles, then continues
down the leg. It eventually branches into two nerves, the Medial
Dorsal Cutaneous Nerve and the Intermediate Dorsal Cutaneous
The first branch off the Tibial
Nerve is the
Sural Cutaneous Nerve, which as mentioned
above, connects with the Lateral Sural Cutaneous Nerve (a branch of the Common
Peroneal Nerve) to form the Sural Nerve.
The Tibial Nerve then supplies
the nervous function to the muscles in the back of the leg--the Popliteus,
Flexor Digitorum Longus
and Flexor Hallucis Longus
muscles. The Tibial Nerve then continues down the back of the leg towards
the ankle and foot.
Nerves of the Ankle Region
There are five major nerves
heading from the leg that impact the foot--the Sural Nerve, the Saphenous Nerve,
the Tibial Nerve, the Deep Peroneal Nerve, and the Superficial Peroneal
Nerve crosses behind the lateral
malleolus (the bump on the outside portion of the ankle). Once in the
foot, the Sural Nerve's name changes to the Lateral
Dorsal Cutaneous Nerve, and it supplies
the sensory information back to the brain concerning the outside edge of the
foot, including the small toe.
Nerve crosses behind the medial
malleolus (the bump on the inside portion of the ankle). This nerve
retains its name and supplies the sensory information back to the brain
concerning the inside edge of the foot including the small toe.
Tibial Nerve crosses the ankle behind
the medial malleolus (the bump on the inside portion of the ankle). It has
Nerve--The Medial Calcaneal Nerve is the
smallest branch. It run along the medial (inside) portion of the heel, and
it provides the sensory innervation
for that portion of the heel.
Plantar Nerve--The Medial Plantar Nerve is the
larger of the two major nerves on the bottom of the foot. (See diagram
below.) The fibres that make
up this nerve originate at the S2-S3 level.
Medial Plantar Nerve gives sensory perception to the
bottom of the big toe, the second and third toes and half of the fourth toe, as
well as the medial (inside) 2/3's of the the bottom of the foot. This
nerve provides innervation (nerve connection) with the Flexor Digitorum Brevis
(FDB), Flexor Hallucis Brevis (FHB),
Lateral Plantar Nerve is the smaller of the two nerves on the bottom of the
foot. (See diagram to the right.) As with the Medial Plantar Nerve, The fibers that make up the
Lateral Plantar Nerve left the spine at the S2-S3 level. The Lateral Plantar Nerves
provides sensory perception to the the outside 1/3 of the bottom of the foot,
including the fifth toe and half of the fourth toe. It innervates the Quadratus
Plantae, Abductor Digiti
Quinti, Flexor Digiti Quinti
Brevis, 1st, 2nd, 3rd and
4th Dorsal Interossei, the 1st, 2nd and 3rd Plantar Interossei and the 2nd, 3rd
and 4th Lumbrical muscles.
We should probably mention
here that a branch from the medial plantar nerve with a branch from the lateral
plantar nerve join together in the fourth interspace of the foot, and this is
the primary location for a neuroma to develop. For more information about
neuromas, please visit our web page by clicking on the word
Deep Peroneal Nerve (also known as
the Anterior Tibial Nerve) passes on the front of the ankle. It divides
into the medial and lateral branches. The medial
branch advances down the foot and supplies
nervous sensation to the space between the big toe and second toe. The lateral
branch supplies the nervous input to the Extensor
Digitorum Brevis muscle, then divides into
three branches which supply the nervous input to the 2nd,
3rd and 4th Interosseous muscles.