Muscles of the Lower Extremity
Muscle: Abductor digit
quinti
Body Part: Toe
Action: Small toe abduction.
Location: At the lateral border of the foot, locate the prominence
of the base of the fifth metatarsal. Insert the electrode immediately
proximal and to the plantar side of the prominence, parallel to the long
axis of the foot.
BTX-A Dose:
BTX-B Dose:
Notes: Caution: deeper insertion leads to the flexor digit quinti or
flexor digitorum brevis with identical innervation.
The abductor digit quinti is superficial and mor susceptible to accumulated
trauma. Consider the first dorsal interosseus if screening for a
foot intrinsice axonal polyneuropathy.
Root: S1, S2
Nerve: Tibial n., lateral plantar branch
Clinical Situation:
Muscle: Abductor hallucis
Body Part: Foot / Toe
Action: Toe abduction
Location: Halfway between the navicular bone prominence, and plane
of the sole, where it is most superficial, insert the needle parallel to
the long axis of the foot.
BTX-A Dose:
BTX-B Dose:
Notes: This superficial muscle is susceptible to trauma. Consider
FDI for polyneuropathy screens.
Root: S1, S2
Nerve: Tibial n., Medial plantar branch
Clinical Situation:
Muscle: Adductor longus
Body Part: Lower extremity
Action: Thigh adduction
Location: Proximal 20% of the thigh, one quarter distance from the
medial border to the anterior border of the thigh
BTX-A Dose:
BTX-B Dose:
Notes: The adductor longus is no longer superficial in the distal portion.
Deep to this is the adductor magnus, which is innervated by the sciatic
n.
Root: (L2), L3, L4
Nerve: Obturator
Clinical Situation:
Muscle: Adductor magnus
Body Part: Lower extremity Thigh
Action: Thigh adduction
Location: With patient supine, thigh externally rotated and abducted,
inject at the upper one-third of the thigh, immediately posterior to the
medial border
BTX-A Dose:
BTX-B Dose:
Notes: Anterior to this is the gracilis, posterior to this is the medial
hamstring
Root: (L2), L3, L4
Nerve: Obturator and sciatic
Clinical Situation:
Muscle: Anterior tibialis
Body Part: Lower extremity
Action: Ankle dorsiflexion. Extensor digitorum longus can produce
the same action and can be eliminated by holding the toes in plantarflexion
while the patient is dorsiflexing the ankle.
Location: One fourth the distance from the tibial shaft to the lateral
order of the leg, at the junction of the middle and upper thirds of the
leg. At this location, this is the only muscle encountered.
BTX-A Dose:
BTX-B Dose:
Notes: Caution: Extensor digitorum longus lies lateral.
Root: (L4), L5
Nerve: Peroneal n. Deep branch.
Clinical Situation:
Muscle: Extensor digitorum
longus
Body Part: Lower extremity
Action: Extension of digits 2 through 5
Location: At the junction of the upper and middle thirds of the leg,
halfway between the tibial shaft and lateral border of the leg. At
this point, the EDL is the first muscle encountered
BTX-A Dose:
BTX-B Dose:
Notes: Neighboring muscles are tibialis anterior anteriorly.
Deep to this is the extensor hallucis longus.
Root: L5, (S1)
Nerve: Peroneal n. deep branch
Clinical Situation:
Muscle: Extensor hallucis
longus
Body Part: Lower extremity
Action: Great toe extension
Location: At the junction of the middle and lower thirds of the leg.
one-third the distance from the tibial shaft to the lateral border of the
leg. Insert electrode deep and medially.
BTX-A Dose:
BTX-B Dose:
Notes: Lateral to this is the extensor digitorum longus.
Deep to this is the interosseous membrane and deeper is the posterior
tibialis.
The muscle is oriented vertically and the tendon of the anterior tibialis
is medial to it.
Root: L5, (S1)
Nerve: Peroneal n. deep branch
Clinical Situation:
Muscle: First dorsal
interosseous
Body Part: Lower extremity (foot)
Action: Fan or curl toes
Location: Point index finger between first and second toes in the dorsal
web space and pull back proximally until it is wedged between the two metatarsal
heads. Insert the needle immediately distal to the finger and angle
slightly toward the second toe. The muscle is at the depth of the
metatarsals.
BTX-A Dose:
BTX-B Dose:
Notes: In chronic neuropathic conditions, the muscle often is atrophic.
Deep to this are the flexor muscles on the plantar side.
Root: S1, S2
Nerve: Tibial n. lateral branch
Clinical Situation:
Muscle: Gastrocnemius,
lateral head
Body Part: Leg
Action: Ankle plantarflexion
Location: Midway between the fibular head and the posterior midline
of the leg. Superficial
BTX-A Dose:
BTX-B Dose:
Notes: Deep to this is the soleus. The medial head is usually
accessible while supine and is more often used.
Root: S1, (S2)
Nerve: Tibial n.
Clinical Situation:
Muscle: Gastrocnemius,
medial head
Body Part: Leg
Action: ankle plantarflexion
Location: Medial border of the leg, junction between the middle and
upper two thirds. Superficial.
BTX-A Dose:
BTX-B Dose:
Notes: Anterior and deep to this is the soleus.
Root: (L5), S1, (S2)
Nerve: Tibial n.
Clinical Situation:
Muscle: Gluteus maximus
Body Part: Hip girdle
Action: Hip extension and abduction. Action is isolated when
knee is flexed 90 degrees
Location: Midpoint of the line connecting the posterior inferior iliac
spine and the greater trochanter. The gluteus maximus is the
first muscle underlying the subcutaneous tissue. Note that the sciatic
nerve is distal and medial to the injection site.
BTX-A Dose:
BTX-B Dose:
Notes: In obese patients, approach the muscle adjacent to the superior
aspect of the gluteal crease.
Root:
Nerve:
Clinical Situation:
Muscle: Gluteus medius
Body Part: Hip girdle
Action: Internal rotation of the thigh.
Location: Electrode is inserted parallel to the anterior border which
is defined by the line from the anterior superior iliac spine to the greater
trochanter.
BTX-A Dose:
BTX-B Dose:
Notes: Anterior to this is the tensor fascia lata, which shares the
same nerve supply.
Root: (L4), L5, (S1)
Nerve: Superior gluteal n.
Clinical Situation:
Muscle: Gracilis
Body Part: Thigh
Action: Thigh adduction
Location: At the junction of the upper and middle thirds, directly
medial.
BTX-A Dose:
BTX-B Dose:
Notes: Posterior border is formed by the adductor magnus, which is
partly supplied by the sciatic n. Distal and posterior borders are
formed by the medial hamstrings. Distal and anterior will be the
vasus medialis or sartorius, both femoral nerve supplied
Root: L2, L3, L4
Nerve: Obturator n.
Clinical Situation:
Muscle: Hamstring
external, biceps femoris long head
Body Part: Thigh
Action: Knee flexion
Location: With patient prone, needle is inserted posterior to the groove
formed from the iliotibial band between the vasus lateralis and the external
hamstrings, parallel to the femur. The long head is the first muscle
reached
BTX-A Dose:
BTX-B Dose:
Notes:
Root: (L5), S1, (S2)
Nerve: Sciatic n. Tibial portion
Clinical Situation:
Muscle: Hamstring
external, biceps femoris short head
Body Part: Thigh
Action: Knee flexion
Location: At the level of the superior crease of the poplieal fossa,
immediately medial or lateral to the tendon of the bieps femoris long head.
Direct the needle down and under the tendon. At this level the short head
is muscular and the long is tendinous.
BTX-A Dose:
BTX-B Dose:
Notes: The more distal insertion assures muscular portion of the long
head is avoided. This muscle is useful for localizing peroneal nerve
injury to the regio of the fibular head, where this muscle is spared.
Root: L5, (S1)
Nerve: Sciatic n., peroneal portion
Clinical Situation:
Muscle: Hamstring internal, smimembranosus
and semitendinosus
Body Part: Thigh
Action: Knee flexion
Location: At mid thigh, at or just medial to the midline and immediately
subcutaneous.
BTX-A Dose:
BTX-B Dose:
Notes:
Root: (L4), L5, (S1), (S2)
Nerve: Sciatic n. Tibial portion
Clinical Situation:
Muscle: Iliopsoas
Body Part: Hip
Action: Hip flexion
Location: Immediately distal to the inguinal ligament, halfwa between
the femoral artery pulse and the anterior superior iliac spine, The electrode
is directed laterally, away form the neurovascular bundle
BTX-A Dose:
BTX-B Dose:
Notes: The iliacus portion of the msucle is examined with this approach
Root: L2, L3
Nerve: Femoral n.
Clinical Situation:
Muscle: Peroneus longus
Body Part: Ankle
Action: Eversion/plantarflexion of the ankle
Location: Straddle the fibular head with index and middle fingers,
pointing proximally. Slide down to the junction between the upper
and middle third of the leg.
BTX-A Dose:
BTX-B Dose:
Notes: extensor digitorum longus lies anterior (and ankle dorsiflexes
and is innervated by the deep branch of the peroneal nerve). In obese
patients, direct toward the lateral border of the leg at the junction between
the upper and middle third.
Root: L5, (S1)
Nerve: Peroneal n. superficial branch
Clinical Situation:
Muscle: Posterior tibialis
Body Part: Ankle
Action: Plantarflexion and inversion of the ankle
Location: At the junction of the middle and lower thirds of the leg,
insert the needle along the medial border of the tibial shaft. The
full width of the flexor digitorum longus is traversed. Alternatively,
approach by the lateral border of the tibia, piercing both anterior tibialis
and interosseous membrane.
BTX-A Dose:
BTX-B Dose:
Notes: The second approach is more reliable. A longer needle
is usually needed (>1.5 in)
Root: L5, (S1)
Nerve: Tibial n.
Clinical Situation:
Muscle: Quadriceps,
rectus femoris
Body Part: Knee
Action: Knee extension
Location: At the midpoint between the anterior superior iliac spine
and the superior pole of the patella
BTX-A Dose:
BTX-B Dose:
Notes: Sartorius, also supplied by the femoral n, lies more proximally,
immediately distal to the ASIS.
Root: L2, L3, L4
Nerve: Femoral n.
Clinical Situation:
Muscle: Quadriceps,
vastus lateralis
Body Part: Thigh
Action: Knee extension, have the patient push the back of the knee
into the table
Location: Mid-thigh, directly lateral, insert needle just anterior
to the groove between the external hamstring group and the vastus lateralis.
BTX-A Dose:
BTX-B Dose:
Notes:
Root: L2, L3, L4
Nerve: Femoral
Clinical Situation:
Muscle: Quadriceps,
vastus medialis
Body Part: Thigh
Action: Knee extension
Location: Distal fifth of the medial thigh. Angle needle parallel
to the fibers which run 45 degrees laterally toward the patella
BTX-A Dose:
BTX-B Dose:
Notes: proximal and posterior are the medial hamstring and adductor
magnus, innervated by different nerves. In thin or cachetic patients
the vastus is often atrophic
Root: L2, L3, L4
Nerve: Femoral
Clinical Situation:
Muscle: Soleus
Body Part: LEg
Action: Ankle plantarflexion, particularly when the knee is flexed
Location: At the junction of the middle and lower third of the leg,
insert immediately adjacent medially or laterally to the posterior midline.
BTX-A Dose:
BTX-B Dose:
Notes: At the midline lies the gastroc tendon. The muscle bellies of
the gastroc end at midpoint above the leg.
Root: S1, (S2)
Nerve: Tibial n.
Clinical Situation: