Peripheral Nerve Injury (Lower Limb) - Basic Anatomy

1. Peripheral Nerve Injury
(Lower Limb)
Dr Sandip Biswas

2. Femoral Nerve
Formed by: Ventral rami of posterior division of L2-4
Root Value: L2-4
Motor Supply: Hip Flexor (iliacus, Sartorius, Pectineus),
Knee Extensor(Quadriceps)
Sensory Supply: Antero-medial thigh and antero-medial
leg and foot (Saphenous Nerve)
Course:
 The nerve descends in the abdomen from Lumbar
Plexus through Psoas Major muscle.
 The nerve further travels downs into the thigh
behind the mid-inguinal point.
 It divides into anterior and posterior branches which
supply hip flexor and knee extensor respectively.

3.  Injury can happen in – direct trauma, anterior hip dislocation, iatrogenic
 Problems after injury-
 Loss of Knee extension
 Mild loss of hip flexion
 Motor function test of femoral nerve
 Quadriceps: Knee Extension
 Sensory Test:
 Anteromedial aspect of thigh
 Anteromedial aspect of leg via Saphenous nerve
Note:
Meralgia Paresthetica- compression of lateral cutaneous nerve of thigh below ASIS under the inguinal
ligament. It causes paraesthesia over lateral aspect of thigh

4. Sciatic Nerve
Formed by: Anterior and posterior divisions of
lumbosacral plexus
Root value- L4-S3
Motor Supply-
 knee flexors(semitendinosus, semimembranosus, biceps femoris
and adductor magnus).
 Later, it supplies muscles of entire leg and foot after dividing into
common peroneal and tibial nerves
Course-
 After exiting from the greater sciatic notch, the
nerve descends in the gluteal region below the
pyriformis behind the hip joint.
 It lies over the external rotators of hip and further
descends into the thigh under the deep head of
biceps femoris.
 In the posterior thigh, the ‘tibial component’ of
sciatic nerve supplies hamstrings.
 At the apex of the popliteal fossa, it divides into
common peroneal and tibial component.

5.  Injury can happen in- Posterior dislocation of hip, posterior surgical approaches to hip, direct trauma,
injection into the gluteal region
 Problems after the injury :
 Loss of knee flexion
 Loss of all motor activity at ankle and foot (flail foot)
 Motor Function Test of sciatic nerve:
 Hamstrings: Knee Flexion
 Test for all ankle and foot muscles
 Sensory test
 Test the sensory function of Tibial and Common Peroneal Nerve

6. Common Peroneal Nerve
Root Value: Dorsal component of L4-S2
Motor Supply: Anterior comp( Tibialis Anterior, Extensor
Hallucis Longus, Extensor digitorum longus, and peroneus
tertius), and Lateral Comp ( Peroneus longus and brevis)
of leg
Sensory Supply:
 Superficial Peroneal Nerve: dorsum of foot except for
1st interdigital cleft, medial and lateral borders of
foot
 Deep Peroneal Nerve: 1st interdigital cleft
Course:
 descends distally along the laterally wall of the
popliteal fossa under the belly of Biceps Femoris.
 Further, it winds around the neck of fibula between
the peroneus longus and bone and divides into
superficial and deep peroneal nerve.
 Superficial peroneal nerve supplies lateral
compartment while deep peroneal nerve supplies
anterior compartment muscles

7.  Injury to CPN nerve can happen in – Fibular Neck Fracture, Knee Dislocation
 Problems after injury to CPN: “FOOT DROP”
 Loss of ankle dorsiflexion(tibialis anterior) and eversion (peroneal longus and brevis)
 Loss of great and lesser toe extension (EHL and EDL)
 High stepping Gait
 Motor function test :
 Tibialis anterior: dorsiflexion in inversion
 EHL,EDL: Extension of great toe and other digits
 Peroneus Longus and brevis: Eversion at subtalar joint
 Sensory Test
 Dorsum of 1st web space: deep peroneal nerve
 Rest of the dorsum: superficial peroneal nerve

8. Tibial Nerve
Root Value- Ventral component of L4-S3
Motor Supply: All muscles of the posterior
compartment of leg and plantar aspect of foot
Sensory Supply- Plantar aspect of foot via medial
and lateral plantar nerves
Course:
 It descends distally in the center of popliteal
fossa and enters the leg under the arch of
soleus.
 In popliteal fossa, it supplies gastrocnemius,
popliteus, plantaris, and soleus.
 Further, it descends and goes behind the
medial malleolus under the flexor retinaculum
and it enters the foot.
 It divides into medial and lateral plantar
nerves and supplies the entire four layers of
foot muscles along with skin of plantar region.

9.  Injury to tibial nerve can happen in- knee dislocation, proximal tibia fractures, compartment syndrome,
compressive neuropathy under the flexor retinaculum
 Problems after the injury :
 Loss of ankle plantar flexion (gastrosoleus)
 Weak inversion (tibialis posterior)
 Loss of plantar flexion of toes
 Claw toes: occurs after injury to the posterior tibial nerve near ankle leading to palsy of all foot intrinsic
muscles
 High stepping gait
 Motor Function test :
 Tendoachilles: ankle plantar flexion while standing on tip toe
 Tibialis posterior: inversion in plantar flexion
 Great toe flexor hallucis longus(FHL) and lesser toe Flexor Digitorum Longus (FDL) plantar flexion
 Sensory Test
 Sensory over the plantar aspect of foot
 Note: Tarsal Tunnel Syndrome- Compression of tibial nerve under the flexor retinaculum behind the ankle