Innervation of the Lower Limb

Question 1

major functions of the lower limb

Answer 1

weight bearing
maintaining posture
locomotion

Question 2

regions of the lower limb

Answer 2

hip (gluteal)
thigh
knee
leg
ankle
foot

Question 3

key bones of the lower limb

Answer 3

pelvic bone
sacrum
(hip joint)
femur
(knee joint)
tibia
fibula

Question 4

key bones of the foot

Answer 4

calcaneus
talus
metatarsals
phalanges

Question 5

bones involved in joints:
hip
knee
ankle
sub-talar
metatarsophalangeal
interphalangeal (PIP and DIP)

Answer 5

hip: pelvis and femur
knee: femur and tibia
ankle: tibia, fibula and talus
sub-talar: talus and calcaneus
metatarsophalangeal: metatarsal and phalanges
interphalangeal: phalanges

Question 6

motions at each joint
hip
knee
ankle
subtalar

Answer 6

hip: extra/intra rotation, abduction/adduction
knee: flexion/extension
ankle: plantar/dorsi-flexion
subtalar: inversion/eversion, adduction/abduction

Question 7

nerves of the lower limb

Answer 7

femoral nerve
obturator nerve
sciatic nerve
tibial nerve
common peroneal nerve (deep and superficial)

Question 8

femoral nerve pathway and motor supply

Answer 8

L2-4
arises from lumbar plexus within psoas major
passes between iliacus and psoas major muscles in the abdomen
enters thigh by passing behind inguinal ligament

supplies muscles of the anterior compartment of thigh

Question 9

sensory branches of femoral nerve and the regions they supply

Answer 9

anterior femoral cutaneous nerve: skin on the front of thigh, knee and medial aspect of thigh

saphenous nerve: skin on the medial of the knee, leg and foot

Question 10

knee jerk reflex

Answer 10

stretching quadricep femoris causes femoral nerve to sense it and contract quads and relax hamstrings
involves L2, L3, L4

Question 11

effect of injury of femoral nerve

Answer 11

may occur with haematomas in iliacus muscle, surgery or pelvic fracture
loss of extension at knee joint and impaired hip flexion
sensory loss over anterior thigh, knee and medial thigh, leg and foot

Question 12

obturator nerve pathway and motor supply

Answer 12

arises from lumbar plexus (L2-L4)
descends in psoas major muscle then along lateral pelvic wall
passes through the obturator foramen

supplies muscles in medial compartment of thigh

Question 13

obturator nerve sensory supply

Answer 13

skin on the inferomedial aspect of the thigh

Question 14

effect of injury to obturator nerve

what may cause it

Answer 14

weakness of thigh adduction
sensory loss over inferomedial thigh

may be caused by pelvic fractures, hip replacement surgery, obturator hernias

Question 15

sciatic nerve pathway and motor supply

Answer 15

arises from L4-S3 from lumbosacral plexus
leaves pelvis via greater sciatic foramen and enters gluteal region
descends into posterior compartment of thigh
divides near the back of the knee into tibial nerve and common peroneal nerve

supplies muscles of posterior compartment of thigh

Question 16

sensory supply at posterior thigh area
where does the nerve originate

Answer 16

posterior cutaneous nerve
arises from S1-3 from sacral plexus
branches from sciatic nerve

Question 17

effect of injury to sciatic nerve

possible causes

Answer 17

loss of knee flexion and impaired hip extension
loss of dorsiflexion and plantarflexion, inversion and eversion of the foot
sensory loss over lateral leg and whole foot

injections to gluteus maximus, hip trauma or surgery, prolonged pressure due to immobility

Question 18

tibial nerve pathway and motor supply

Answer 18

descends through the popliteal fossa
passes into the back of the leg
gives out a branch into sural nerve
tibial nerve passes behind medial malleolus into the foot and divides into plantar nerves

supplies all the muscles in the posterior compartment

Question 19

effect of injury to tibial nerve
possible causes

Answer 19

loss of plantarflexion of the foot and flexion of the toes
sensory loss over posterolateral leg, sole and lateral aspect of foot

may be caused by compression due to Baker’s cyst or foot and ankle trauma

Question 20

common peroneal nerve pathway

Answer 20

L4-S2
arises as terminal portion of sciatic nerve in popliteal fossa
descends laterally and winds around neck of fibula
divides into superficial and deep peroneal nerves

Question 21

superficial peroneal nerve motor supply

Answer 21

muscles of lateral compartment of leg

Question 22

deep peroneal nerve motor supply

Answer 22

muscles of anterior compartment of leg

Question 23

superficial and deep peroneal nerve sensory supply

Answer 23

superficial: skin of anterolateral leg and dorsum of the foot (top)
except between first two toes

deep: skin of the space between first two toes

Question 24

common peroneal nerve effect of injury
common causes

Answer 24

foot drop: loss of dorsiflexion and eversion
loss of sensation on anterolateral aspect of leg and dorsum of foot

fracture of neck of the fibula