Lower Extremity Nerves

What are the lower three nerves of the lumbar plexus that go to the lower extremities?

- lateral femoral cutaneous nerve (L2-L3)

- femoral nerve (L2-L4)

- obturator nerve (L2-L4)

What does the L5 spinal nerve contribute to?

the sacral plexus

What spinal roots does the lateral femoral cutaneous nerve arise from?

L2 and L3

How does the lateral femoral cutaneous nerve enter the lower extremity?

enters the lateral thigh going under the lateral inguinal ligament at the lateral aspect of the inguinal arch

What type of innervation does the lateral femoral cutaneous nerve supply?

sensory for the lateral thigh

What might happen as the lateral femoral cutaneous nerve travels over the iliac bone?

potential compression or entrapment

What might lead to entrapment of the lateral femoral cutaneous nerve?

tight clothes, belts, pregnancy, and excessive weight

Meralgia paresthetica

numbness and tingling in the outer thigh due to entrapment of the lateral femoral cutaneous nerve

What nerve roots does the femoral nerve arise from?

L2, L3, L4

How does the femoral nerve travel into the lower extremity?

passes under the inguinal arch and into the anterior compartment

What does the femoral nerve supply?

most muscles in the anterior compartment of the thigh

What do the muscles in the anterior compartment of the thigh do?

flex the hip joint and extend the knee joint

What is the femoral nerve sensory for?

- anterior medial thigh (anterior cutaneous nerve)

- medial leg and foot (saphenous nerve)

What are the muscles in the anterior compartment of the thigh?

- pectineus

- iliopsoas/psoas major

- psoas minor

- iliacus

- sartorius

- quadriceps femoris

Origin of the pectineus

superior ramus of the pubis

Insertion of the pectineus

pectineal line of the femur

Action of the pectineus

adducts and flexes the hip; medial rotation of the hip

Origin of the iliopsoas/psoas major

sides of the body of vertebrae (T12-L5)

Insertion of the iliopsoas/psoas major

lesser trochanter of the femur

Action of the iliopsoas/psoas major

flex hip; flex trunk

Origin of the psoas minor

sides of T12-L1

Insertion of the psoas minor

iliopectinal eminence of pubis

Action of the psoas minor

flex trunk

Origin of the iliacus

iliac crest, iliac fossa

Insertion of the iliacus

lesser trochanter of the femur

Action of the iliacus

flex hip; flex trunk

Origin of the sartorius

ASIS

Insertion of the sartorius

medial surface of the proximal tibia

Action of the sartorius

flex, abduct, lateral rotate the thigh at the hip; flex knee

Innervation of the pectineus, iliopsoas/psoas major, psoas minor, iliacus, sartorius, and quadriceps femoris

femoral nerve (L2-L3)

What are flexors of the hip innervated by?

femoral nerve

What are adductors of the hip innervated by?

obturator nerve

What is special about pectineus muscle?

it is a flexor and adductor; it is primarily in the flexor compartment and is innervated by the femoral nerve

What muscles make up the quadriceps femoris?

rectus femoris, vastus lateralis, vastus medialis, vastus intermedius

Origin of the rectus femoris

AIIS

Insertion of the rectus femoris

patella via common tendon, tibial tuberosity via patellar ligament

Action of the rectus femoris

extend leg at knee, help flex hip

Origin of the vastus lateralis

greater trochanter, lateral lip linea aspera

Insertion of the vastus lateralis

patella via common tendon, tibial tuberosity via patellar ligament, lateral patellar retinacula to tibia

Origin of the vastus medialis

intertrochanter line, medial lip of linea aspera

Insertion of the vastus medialis

patella via common tendon, tibial tuberosity via patellar ligament, medial patellar retinacula to tibia

Origin of the vastus intermedius

anterior and lateral surface of the shaft of the femur

Insertion of the vastus intermedius

patella via common tendon, tibial tuberosity via patellar ligament

Action of the vastus lateralis, vastus medialis, and vastus intermedius

extend leg at knee

Innervation of the rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius

femoral nerve (L3, L4)

What do anterior compartment muscles that extend past the knee joint do?

extend the leg at the knee (these are all innervated by femoral nerve)

What are common ways in which the femoral nerve might be damaged?

pelvic fracture and pelvic radiation

What would damage to the femoral nerve lead to?

impairment of anterior compartment muscles, muscle wasting, and sensory loss

What might cause damage to the saphenous nerve (branch of femoral nerve)?

surgery involving the great saphenous vein

What surgeries involve the great saphenous vein?

- stripping of varicose veins

- harvesting for cardiac bypass

What does the saphenous nerve supply?

sensory to the medial thigh and leg

What are the two primary sensory branches of the femoral nerve, and what do they cover?

anterior cutaneous branches & saphenous nerve, which cover most of the anterior and medial aspects of the thigh & medial leg

What might femoral nerve damage present as?

paresthesia or spontaneous pain

What does the saphenous nerve travel with?

the great saphenous vein (care must be taken with procedures related to the great saphenous vein)

What nerve roots does the obturator nerve branch from?

L2, L3, L4

What does the obturator nerve innervate?

medial (adductor compartment) of the thigh

What is the obturator nerve sensory for?

upper medial thigh

How does the obturator nerve enter the thigh, and where does it travel?

through the obturator canal; travels between adductor brevus and adductor longus

What are the medial thigh muscles?

- adductor longus

- adductor brevis

- adductor magnus

- gracilis

- obturator externus

Origin of the adductor longus

body of pubis

Insertion of the adductor longus

linea aspera of femur

Origin of the adductor brevis

body and inferior ramus of pubis

Insertion of the adductor brevis

linea aspera of femur

Innervation of the adductor longus & adductor brevis

obturator nerve (L2-L4)

Action of the adductor longus & adductor brevis

adduct thigh

Origin of the adductor magnus

inferior ramus of pubis, ischial tuberosity

Insertion of the adductor magnus

gluteal tuberosity, adductor tubercle

Innervation of the adductor magnus

obturator nerve (L2-L4) & hamstring part sciatic nerve (L4)

Action of the adductor magnus

adducts thigh, flexes thigh, extends thigh

Origin of the gracilis

body and inferior ramus of pubis

Insertion of the gracilis

medial surface of tibia

Innervation of the gracilis

obturator nerve (L2-L3)

Action of the gracilis

adducts thigh, flexes knee, medial rotate leg

Origin of the obturator externus

margin of obturator foramen, obturator membrane

Insertion of the obturator externus

trochanteric fossa

Innervation of the obturator externus

obturator nerve (L3-L4)

Action of the obturator externus

lateral rotate thigh, stabilizes hip joint

How do the medial (adductor) compartment muscles stack?

longus, brevis, magnus (anterior to posterior)

Which adductor muscle is large enough to be easily observable from the posterior compartment?

adductor magnus

What else does the adductor magnus contribute too?

hamstrings, and that part of it receives innervation from the sciatic nerve

What might cause damage to the obturator nerve?

pelvic surgery or pregnancy

What does obturator nerve impairment lead to?

weak adduction and sensory loss to upper medial thigh

What are obturator nerve blocks used for?

pain management with chronic hip pain

What nerve roots does the sciatic nerve arise from?

L4 to S3

What is the upper part of the lumbosacral trunk?

L4 and L5 roots as they descend down into the pelvis to join the sacral plexus

What does the upper part of the lumbosacral trunk join with?

S1, S2, and S3 to make the large sciatic nerve

What are the two parts of the sciatic nerve?

fibular portion & tibial portion

What is the relationship between the gluteal muscles and the sciatic nerve?

the sciatic nerve exits into the gluteal region traveling through the greater sciatic foramen below the piriformis muscle

Where should intramuscular injections into the gluteal region be done, and why?

upper lateral quadrant to avoid damage to the sciatic nerve

Which injection site is preferred: ventrogluteal or dorsogluteal?

ventrogluteal sites are preferred over dorsogluteal

What nerve is responsible for the muscles of the posterior compartment of the thigh?

sciatic nerve (mostly the tibial portion)

What are the posterior thigh muscles collectively known as?

hamstring muscles

What is each hamstring muscle innervated by?

sciatic nerve

What is the function of each hamstring muscle?

extend the thigh

What hamstring muscles extend over the knee joint?

semitendinosus, semimembranosus, biceps femoris long head

All BUT the biceps femoris short head

What is the additional function of the hamstring muscles that extend over the knee joint?

flex the knee

Origin of the semitendinosus and semimembranosus

ischial tuberosity

Insertion of the semitendinosus

medial surface of superior tibia

Insertion of the semimembranosus

posterior surface of the medial tibial condyle

Innervation of the semitendinosus and semimembranosus

tibial division of sciatic nerve (L5-S2)