Evaluation of Nerve Root Lesions Involving the Trunk and Lower Extremity
Manifestations of pathology involving the spinal cord and cauda equina, such as
herniated disks, tumors, or avulsed nerve roots, are frequently found in the lower
extremity. Understanding the clinical relationship between various muscles,
reflexes, and sensory areas in the lower extremity and their neurologic levels
(cord levels) is particularly helpful in detecting and locating spinal problems
with greater accuracy and ease.
To make the relationship between the spine and the lower extremity clear,
the neurologic examination of the lumbar spine is divided into tests of each
neurologic level and its dermatomes and myotomes. Thus, for each neurologic
level of the lower spinal cord, the muscles, reflexes, and the sensory areas that
most clearly receive innervation from it is tested.
Testing of Individual Nerve Roots,
T2-S4
Neurologic Levels T2-T12
Muscle Testing
Intercostals: The intercostal muscles are segmentally innervated and are difficult
to evaluate individually.
Rectus Abdominis: The rectus abdominis muscles are segmentally innervated
by the primary anterior divisions of T5-T12 (L1), with the umbilicus the
dividing point between T10 and T11.
Beevor’s sign (Fig. 2-1) tests the integrity of the segmental innervation of
the rectus abdominis muscles. Ask the patient to do a quarter sit-up. While the
patient is doing this, observe the umbilicus. Normally, it should not move at all
when the maneuver is performed. If, however, the umbilicus is drawn up or
down or to one side or the other, be alerted to possible asymmetrical
involvement of the anterior abdominal muscles. Lesions of the spinal cord or
roots between T10 and T12 will cause weakness of the lower part of the muscle,
and thus a positive Beevor’s side with the umbilicus moving upward during the
quarter sit-up.
FIGURE 2-1 Beevor’s sign.
Sensory Testing
Sensory areas for each nerve root are shown in Figure 4-1. The sensory area for
T4 crosses the nipple line, T7 the xiphoid process, T10 the umbilicus, and T12
the groin. There is sufficient overlap of these areas for no anesthesia to exist if
only one nerve root is involved. However, hypoesthesia is probably present.
Neurologic Levels T12-L3
Muscle Testing
There is no specific muscle test for each root. The muscles that are usually
tested are the iliopsoas (T12-L3), the quadriceps (L2-L4), and the adductor
group (L2-L4).
Iliopsoas: (Branches from [T12], L1-L3): The iliopsoas muscle is the main
flexor of the hip (Fig. 2-2). To test it, instruct the patient to sit on the edge of the
examining table with the legs dangling. Stabilize the pelvis by placing your hand
over the patient’s iliac crest and have the patient actively raise their thigh off the
table. Now place your other hand over thedistal femoral portion of the knee and
ask the patient to raise the thigh further as you resist (Fig. 2-3). Determine the
maximum resistance the patient can overcome. Then repeat the test for the
opposite iliopsoas muscle and compare muscle strengths. Because the iliopsoas
receives innervation from several levels, a muscle that is only slightly weaker
than its counterpart may indicate neurologic problems.
FIGURE 2-2A (T12), L1-L3—hip flexion.
FIGURE 2-2B Iliopsoas.
Origin: Anterior surface of the bodies of all lumbar vertebrae and
their transverse processes and corresponding intervertebral
disks. Upper two-thirds of the iliac fossa.
Insertion: Lesser trochanter of femur.
FIGURE 2-3 Muscle test for the iliopsoas.
In addition to possible neurologic pathology, the iliopsoas may become
weak as a result of an abscess within its substance; the patient may then
complain of pain during muscle testing. The muscle may also become weak as a
result of knee or hip surgery.
Quadriceps: L2- L4 (Femoral Nerve): To test the quadriceps functionally,
instruct the patient to stand from a squatting position (Fig. 2-4). Note carefully
whether the patient stands straight, with the knees in full extension, or whether
one leg is used more than the other. The arc of motion from flexion to extension
should be smooth. Occasionally, the patient may be able to extend the knee
smoothly only until the last 10°, finishing the motion haltingly and with great
effort. This faltering in the last 10° of extension is called extension lag; it occurs
because the last 10° to 15° of knee extension requires at least 50 percent more
muscle power than the rest (according to Jacqueline Perry). Extension lag is
frequently seen in association with quadriceps weakness. Sometimes, the patient
may be unable to extend his knee through the last 10° with even the greatest
effort (Fig. 2-5).
FIGURE 2-4A L2-L4—knee extension.
FIGURE 2-4B Rectus femoris.
Origin: Rectus femoris is a “two-joint” muscle that has two heads
of origin. Straight head: from anterior inferior iliac spine.
Reflected head: from groove just above brim of acetabulum.
Insertion: Upper border of patella, and then into the tibial
tubercle via the infrapatellar tendon.
FIGURE 2-4C Vastus intermedius.
Origin: Upper two-thirds of anterior and lateral surface of femur.
Insertion: Upper border of the patella with the rectus femoris
tendon and then via the infrapatellar tendon into the tibial
tubercle.
Vastus lateralis.
Origin: Capsule of hip joint, intertrochanteric line, gluteal
tuberosity, linea aspera.
Insertion: Proximal and lateral border of patella, and into tibial
tubercle via the infrapatellar tendon.
Vastus medialis.
Origin: Lower half of intertrochanteric line, linea aspera, medial
supracondylar line, medial intermuscular septum, tendon of
adductor magnus.
Insertion: Medial border of patella and into tibial tubercle via the
infrapatellar tendon.
FIGURE 2-5 Extension lag. (Hoppenfeld, S.: Physical
Examination of the Spine and Extremities. Norwalk, CT:
Appleton-Century-Crofts, 1976.)
To test the quadriceps manually, stabilize the thigh by placing one hand just
above the knee. Instruct the patient to extend his knee as you offer resistance
just above the ankle joint. Palpate the quadriceps during the test with your
stabilizing hand (Fig. 2-6). Note that the quadriceps weakness can also be due to
a reflex decrease in muscle strength following knee surgery or to tears within the
substance of the muscle itself.
FIGURE 2-6 Muscle test for the quadriceps.
Hip Adductor Group: L2-L4 (Obturator Nerve): Like the quadriceps, the hip
adductors can be tested as a massive grouping (Fig. 2-7). Have the patient lie
supine or on their side and instruct the patient to abduct the legs. Place your
hand on the medial sides of both knees and have the patient adduct their legs
against your resistance (Fig. 2-8). Determine the maximum resistance they can
overcome.
Reflexes
Although the patellar tendon reflex is supplied by L2-L4, it is predominantly L4
and will be tested as such.
Sensory Testing
Nerves from L1 to L3 provide sensation over the general area of the anterior
thigh between the inguinal ligament and the knee. The L1 dermatome is an
oblique band on the upper anterior portion of the thigh, immediately below the
inguinal ligament. The L3 dermatome is an oblique band on the anterior thigh,
immediately above the kneecap. Between these two bands, on the anterior aspect
of the mid thigh, lies the L2 dermatome (Fig. 2-9).
FIGURE 2-7A L2-L4—hip adduction.
FIGURE 2-7B Adductor brevis (center).
Origin: Outer surface of inferior ramus of pubis.
Insertion: Line extending from lesser trochanter to linea aspera
and upper part of linea aspera.
Adductor longus (left).
Origin: Anterior surface of the pubis in the angle between crest
and pubic symphysis.
Insertion: Linea aspera, middle half of medial lip.
Adductor magnus (right).
Origin: Ischial tuberosity, inferior rami of ischium and pubis.
Insertion: Line extending from greater trochanter to linea aspera.
The entire length of linea aspera, medial supracondylar line, and
adductor tubercle of the femur.
FIGURE 2-8 Muscle test for hip adductors.
Sensory testing, with its bands of individual dermatomes, is a more
accurate way of evaluating neurologic levels T12-L3 than motor testing, which
lacks individual representative muscles. There are also no representative reflexes
for these levels, making it even more difficult to diagnose an exact neurologic
level. Neurologic levels L4, L5, and S1 are represented by individual muscles,
dermatomes, and reflexes, and are easier to diagnose.
Neurologic Level L4
Muscle Testing
Tibialis Anterior: L4 (Deep Peroneal Nerve): The tibialis anterior muscle is
predominantly innervated by the L4 segmental level; it also receives L5
innervation (Figs. 2-10 and 2-11). To test the muscle in function, ask the patient
to walk on his heels with his feet inverted. The tendon of the tibialis anterior
muscle becomes visible as it crosses the anteromedial portion of the ankle joint
and is quite prominent as it proceeds distally toward its insertion. Patients with
weak tibialis anterior muscles are unable to perform this functional dorsiflexion-
inversion test; they may also exhibit “drop foot,” or steppage gait.
FIGURE 2-9 Dermatomes of the lower extremity.
To test the tibialis anterior manually, instruct the patient to sit on the edge
of the examining table. Support his lower leg, and place your thumb in a
position that makes him dorsiflex and invert his foot to reach it. Try to force the
foot into plantar flexion and eversion by pushing against the head and shaft of
the first metatarsal; palpate the tibialis anterior muscle as you test it (Fig. 2-12).
FIGURE 2-10 Neurologic level L4.
FIGURE 2-11A L4, L5—foot inversion.
FIGURE 2-11B Tibialis anterior.
Origin: Lateral condyle of tibia, upper two-thirds of the
anterolateral surface of tibia, interosseusmembrane.
Insertion: Medial and plantar surfaces of medial cuneiform bone,
base of 1st metatarsal bone.
FIGURE 2-12 Muscle test for the tibialis anterior.
Reflex Testing
Patellar Tendon Reflex: The patellar tendon reflex is a deep tendon reflex,
mediated through nerves emanating from the L2-L4 nerve roots (predominantly
from L4). For clinical application, the patellar tendon reflex should be
considered an L4 reflex; however, because it receives innervation from L2 and
L3 as well as from L4, the reflex will still be present, although significantly
weakened, even if the L4 nerve root is completely severed. The reflex is almost
never totally absent. However, in primary muscle, nerve root, or anterior horn
cell disease, the reflex can be totally absent.
FIGURE 2-13 Patellar tendon reflex.
To test the patellar tendon reflex, ask the patient to sit on the edge of the
examining table with the legs dangling. (The patient may also sit on a chair with
one leg crossed over his knee or, if the patient is in bed, with the knee supported
in a few degrees of flexion) (Fig. 2-13). In these positions, the infrapatellar
tendon is stretched and primed. Palpate the soft tissue depression on either side
of the tendon to locate it accurately, and attempt to elicit the reflex by tapping
the tendon at the level of the knee joint with a short, smart wrist action. If the
reflex is difficult to obtain, reinforce it by having the patient clasp his hands and
attempt to pull them apart as you tap the tendon. This is known as the Jendrassik
maneuver. It prevents the patient from consciously inhibiting or influencing his
or her response to reflex testing. Repeat the procedure on the opposite leg, and
grade the reflex as normal, increased, decreased, or absent. To remember the
neurologic level of the reflex, associate the fact that four muscles constitute the
quadriceps muscle with the L4 of the patellar tendon reflex (Fig. 2-14).
The reflex may be affected by problems other than neurologic pathology.
For example, if the quadriceps has been traumatized, if the patient has
undergone recent surgery to the knee, or if there is knee joint effusion, the reflex
may be absent or diminished.
Sensory Testing
The L4 dermatome covers the medial side of the leg and extends to the medial
side of the foot. The knee joint is the dividing line between the L3 dermatome
above and the L4 dermatome below. On the leg, the sharp crest of the tibia is the
dividing line between the L4 dermatome on the medial side and the L5
dermatome on the lateral side (Fig. 2-15).
FIGURE 2-14 An easy way to remember that the patellar tendon
reflex is innervated by L4 is to associate the four quadriceps
muscles with the neurologic level L4.
FIGURE 2-15 L4 and L5 sensory dermatome.
Neurologic Level L5
Muscle Testing (Figs. 2-16 to 2-18)
1. Extensor hallucis longus
2. Extensor digitorum longus and brevis
3. Gluteus medius
FIGURE 2-16 Neurologic level L5.
Extensor Hallucis Longus: L5 (Deep Branch of the Peroneal Nerve): The
tendon of the extensor hallucis longus passes in front of the ankle joint lateral to
the tibialis anterior, which is predominately innervated by L4. Test it
functionally by having the patient walk on his heels, with his feet neither
inverted nor everted. The tendon should stand out clearly on the way to its
insertion at the proximal end of the distal phalanx of the great toe. To test the
extensor hallucis longus manually, have the patient sit on the edge of the table.
Support the foot with one hand around the calcaneus and place your thumb in
such a position that the patient must dorsiflex his great toe to reach it. Oppose
this dorsiflexion by placing your thumb on the nail bed of the great toe and your
fingers on the ball of the foot; then pull down on the toe (Fig. 2-19A). If your
thumb crosses theinterphalangeal joint, you will be testing the extensor hallucis
brevis as well as the longus; make certain that you apply resistance distal to the
interphalangeal joint so that you are testing only the extensor hallucis longus.
Note that a fracture of the great toe or other recent trauma will produce apparent
muscle weakness in the extensor hallucis longus.
Extensor Digitorum Longus and Brevis: L5 (Deep Peroneal Nerve): Test the
extensor digitorum longus in function by instructing the patient to walk on his
heels, as he did for the extensor hallucis longus. The tendon of the extensor
digitorum longus should stand out on the dorsum of the foot, crossing in front of
the ankle mortise and fanning out to insert by slips into the dorsal surfaces of the
middle and distal phalanges of the lateral four toes.
For the manual test, the patient may remain seated on the edge of the table.
Secure the ankle with one hand around the calcaneus and place the thumb of
your free hand in such a position that he must extend his toes to reach it. Oppose
this motion by pressing on the dorsum of the toes and attempting to bend them
plantarward (Fig. 2-19B). They should be virtually unyielding.
FIGURE 2-17 L4, L5—foot dorsiflexion (ankle extension).
FIGURE 2-18A Extensor hallucis longus.
Origin: Middle half of anterior surface of fibula, adjacent
interosseous membrane.
Insertion: Dorsal surface of base of distal phalanx of great toe.
FIGURE 2-18B Extensor digitorum longus.
Origin: Upper three-fourths of anterior surface of fibula,
interosseous membrane.
Insertion: Dorsal surface of middle and distal phalanges of
lateral four toes.
FIGURE 2-18C Extensor digitorum brevis.
Origin: Forepart of upper and lateral surface of calcaneus, sinus
tarsi.
Insertion: First tendon into dorsal surface of base of proximal
phalanx of great toe, remaining three tendons into lateral sides
of tendons of extensor digitorum longus.
FIGURE 2-19A Muscle test of the extensor hallucis longus
muscle.
FIGURE 2-19B Muscle test for toe extensors.
FIGURE 2-19C An easy way to remember that the toe
extensors are innervated by neurologic level L5.
Gluteus Medius: L5 (Superior Gluteal Nerve): To test the gluteus medius,
have the patient lie on his side (Fig. 2-20). Stabilize the patient’s pelvis with one
hand and instruct the patient to abduct the leg. Allow the leg to abduct fully
before you resist by pushing against the lateral thigh at the level of the knee joint
(Fig. 2-21). To prevent the muscle substitution that may take place if the hip is
allowed to flex, make sure it remains in a neutral position throughout the test.
Reflex Testing
There is no easily elicited reflex supplied by the L5 neurologic level. Although
the tibialis posterior muscle provides an L5 reflex, it is difficult to elicit
routinely. If, after you have performed sensory and motor tests, you are not
certain of the integrity of the L5 level, you should try to elicit the tibialis
posterior reflex by holding the forefoot in a few degrees of eversion and
dorsiflexion, and by tapping the tendon of the tibialis posterior muscle on the
medial side of the foot just before it inserts into the navicular tuberosity.
Normally, you should elicit a slight plantar inversion response.
Sensory Testing
The L5 dermatome covers the lateral leg and dorsum of the foot. The crest of the
tibia divides L5 from L4. To make the distinction between L4 and L5 clearer,
palpate the crest of the tibia from the knee distally as it angles toward the medial
malleolus. All that is lateral to the crest, including the dorsum of the foot,
receives sensory innervation from L5 (see Fig. 2-15).
Neurologic Level S1
Muscle Testing
1. Peroneus longus and brevis
2. Gastrocnemius-soleus muscles
3. Gluteus maximus
Peroneus Longus and Brevis: S1 (Superficial Peroneal Nerve): The
peronei may be tested together in function (Figs. 2-22 and 2-23). Because they
are evertors of the ankle and foot, ask the patient to walk on the medial borders
of his feet. The peronei tendons should become prominent just before they turn
around the lateral malleolus, pass on either side of the peroneal tubercle (the
brevis above, the longus below), and run to their respective insertions.
FIGURE 2-20 L4, L5, S1—hip abduction.
FIGURE 2-21A Gluteus medius.
Origin: Outer surface of ilium between iliac crest and posterior
gluteal line above to the anterior gluteal line below, as well as
the gluteal aponeurosis.
Insertion: Lateral surface of greater trochanter.
FIGURE 2-21B Muscle test for the gluteus medius muscle.
FIGURE 2-22 Neurologic level S1.
To test the peronei muscles manually, have the patient sit on the edge of the
table. Secure the ankle by stabilizing the calcaneus and place your other hand in
a position that forces him to plantarflex and evert his foot to reach it with his
small toe. Oppose this plantar flexion and eversion by pushing against the head
and shaft of the 5th metatarsal bone with the palm of your hand (Fig. 2-24);
avoid applying pressure to the toes, because they may move.
FIGURE 2-23 S1—foot eversion.
FIGURE 2-24A Peroneus longus.
Origin: Head and proximal two-thirds of lateral surface of fibula.
Insertion: Lateral side of medial cuneiform bone, base of 1st
metatarsal bone.
Peroneus brevis.
Origin: Distal two-thirds of lateral surface of fibula, adjacent
intermuscular septa.
Insertion: Styloid process of base of 5th metatarsal bone.
FIGURE 2-24B Muscle test for the peronei muscles.
Gastrocnemius-Soleus Muscles: S1, S2 (Tibial Nerve): Because the
gastrocnemius-soleus group is far stronger than the combined muscles of your
arm and forearm, it is difficult to detect small amounts of existing weakness; the
group is thus a poor choice for manual muscle testing and should be observed in
function (Fig. 2-25). Ask the patient to walk on his toes; the patient will be
unable to do so if there is gross muscle weakness. If the test is normal, instruct
him to jump up and down on the balls of his feet, one at a time, forcing the calf
muscles to support almost two-and-a-half times the body’s weight. If the patient
lands flat-footed or is otherwise incapable of performing this test, there is
weakness in the calf muscle (Fig. 2-26). Obviously, elderly people or patients
with back pain cannot be expected to perform this portion of the functional test.
Ask these patients to stand on one leg and rise up on their toes five times in
succession. Inability to complete this test indicates calf muscle weakness.
FIGURE 2-25 L5, S1, S2—foot plantar flexion (ankle flexion).
FIGURE 2-26A Gastrocnemius.
Origin: Medial head: from medial condyle and adjacent part of
femur. Lateral head: from lateral condyle and adjacent part of
femur.
Insertion: Into posterior surface of calcaneus by calcaneal
tendon (Achilles tendon).
FIGURE 2-26B Soleus.
Origin: Posterior surface of head and upper third of the fibula,
popliteal and middle third of medial border of tibia, tendinous
arch between tibia and fibula.
Insertion: Into posterior surface calcaneus by calcaneal tendon.
FIGURE 2-26C Muscle test for the gastrocnemius-soleus
muscle group.
Gluteus Maximus: S1 (Inferior Gluteal Nerve): To test the gluteus maximus
functionally, have the patient stand from a sitting position without using his
hands (Fig. 2-27). To test it more accurately for strength, ask him to lie prone on
the examining table with his hips flexed over the edge and his legs dangling.
Have the patient bend their knee to relax the hamstring muscles so that they
cannot assist the gluteus maximus in hip extension. Place your forearm over his
iliac crest to stabilize the pelvis, leaving your hand free to palpate the gluteus
maximus muscle. Then ask him to extend his hip. Offer resistance to hip
extension by pushing down on the posterior aspect of his thigh just above the
knee joint; as you perform the test, palpate the gluteus maximus muscle for tone
(Fig. 2-28).
Reflex Testing
Achilles Tendon Reflex: The Achilles tendon reflex is a deep tendon reflex,
mediated through the triceps surae. It is supplied predominantly by nerves
emanating from the S1 cord level. If the S1 root is cut, the Achilles tendon
reflex will be virtually absent.
To test the Achilles tendon reflex, ask the patient to sit on the edge of the
examining table with the legs dangling. Put the tendon into slight stretch by
gently dorsiflexing the foot. Place your thumb and fingers into the soft tissue
depressions on either side to locate the Achilles tendon accurately, and strike it
with the flat end of a neurologic hammer to induce a sudden, involuntary plantar
flexion of the foot (Fig. 2-29). It may be helpful to reinforce the reflex by having
the patient clasp his hands and try to pull them apart (or push them together) just
as the tendon is being struck. To remember the S1 reflex more easily, associate
“AchilleS’1 weak spot” with the reflex (Fig. 2-30).
There are various alternate methods of testing the Achilles tendon reflex,
some of which are described here. Choose the appropriate method, depending on
the condition of the particular patient you are examining.
If the patient is bedridden, cross one leg over the opposite knee so that
movement of the ankle joint is unhindered. Prime the tendon by slightly
dorsiflexing the foot with one hand on the ball of the foot and strike the tendon.
If the patient is lying prone in bed, ask the patient to flex the knee to 90° and
prime the tendon by slightly dorsiflexing the foot before performing the test. If
the patients ankle joint is swollen, or if it is prohibitively painful to tap the
Achilles tendon directly, have the patient lie prone with the ankle over the edge
of the bed or examining table. Press the forepart of your fingers against the ball
of the foot to dorsiflex it and strike your fingers with the neurologic hammer. A
positive reflex is present if the gastrocnemius muscle contracts and the foot
plantar flexes slightly. You should be able to detect this motion through your
hand.
FIGURE 2-27 S1—hip extension.
FIGURE 2-28A Gluteus maximus.
Origin: Posterior gluteal line and lateral lip of iliac crest, posterior
surface of sacrum and coccyx.
Insertion: Iliotibial band of fascia lata, gluteal tuberosity offemur.
FIGURE 2-28B Muscle test for the gluteus maximus.
FIGURE 2-28C S1 dermatome.
FIGURE 2-29 Test of the tendon of Achilles reflex.
Sensory Testing
The S1 dermatome covers the lateral side and a portion of the plantar surface of
the foot (Fig. 2-28C).
Neurologic Levels S2-S4
Nerves emanating from the S2 and S3 neurologic levels supply the intrinsic
muscles of the foot. Although there is no efficient way to isolate these muscles
for testing, you should inspect the toes for clawing, possibly caused by
denervation of the intrinsics. S2-S4 are also the principal motor supply to the
bladder, and neurologic problems that affect the foot may affect it as well.
Reflex Testing
Note that there is no deep reflex supplied by S2-S4. There is, however, a
superficial anal reflex. To test it, touch the perianal skin; the anal sphincter
muscle (S2-S4) should contract (wink) in response.
FIGURE 2-30 An easy way to remember that the tendon of
Achilles reflex is an S1 reflex.
Sensory Testing
The dermatomes around the anus are arranged in three concentric rings,
receiving innervation from S2 (outermost ring), S3 (middle ring), and S4-S5
(innermost ring) (Fig. 2-31).
Summary
The following is a suggested clinical scheme for most neurologic level testing in
the lower extremity. It is practical to evaluate all motor power first, then all
sensation, and finally all reflexes.
Most muscle testing of the involved lower extremity can be performed
with a minimum of effort and motion for examiner and patient if it is generally
confined to the foot. Muscle test across the foot from the medial to the lateral
side; the tibialis anterior on the medial side of the foot is innervated by L4, the
extensor digitorum longus and brevis on the top of the foot by L5, and the
peronei on the lateral side of the foot by S1.
FIGURE 2-31 Sensory dermatomes S2-S5.
Sensation can also be tested in a smooth, continuous pattern across the
dorsum of the foot from medial to lateral. The medial border of the foot receives
innervation from L4, the top of the foot from L5, and the lateral border of the
foot from S1 (Fig. 2-32). It is practical to test sensation in each extremity
simultaneously to obtain instant comparison. The skin over a muscle is usually
innervated by the same neurologic level as the muscle it covers.
FIGURE 2-32 The sensory dermatomes (A) and (B) a practical
method of testing sensation across the dorsum of the foot.
Reflexes can be tested smoothly as well. With the patient seated, the
appropriate tendons—infrapatellar tendon, L4; tendon of Achilles, S1—are
easily tested.
NEUROLOGIC LEVELS IN UPPER EXTREMITY
Motor
L3—Quadriceps (L2-L4)
L4—Tibialis anterior
L5—Toe extensors
S1—Peronei
Sensation
T12—Lower abdomen just proximal to inguinal ligament
L1—Upper thigh just distal to inguinal ligament
L2—Mid thigh
L3—Lower thigh
L4—Medial leg—medial side of foot
L5—Lateral leg—dorsum of foot
S1—Lateral side of foot
