Nerves of the Leg

Lumbrosacral Plexus (General)

major nerves of leg

two plexuses

• lumbar plexus

• sacral plexus

include

• femoral n

• obturator n

• sciatic n

• superior gluteal n

• inferior gluteal n

Lumbrosacral Plexus Origin+Exit

originate at

• lumbrosacral plexus

• plexus of nerves on posteiror wall of abdomen+posterior wall of pelvis

exit

• abdomen

• pelvis

Lumbar Plexus Innervation

anterior rami of l1-l3

part of l4→anterior ramus

Lumbosacral Trunk

last half of anteiror ramus l4+anterior ramus l5→enters pelvic cavity→joins with anterior rami s1-s3+part of s4→forms sacral plexus

Femoral Nerve Contributions+Innervations

contributions→l2-l4

innervation→all muscles on anterior compartment of thigh

Femoral Nerve Exit+Enter

exits→pelvis via gap between inguinal ligament+superior margin of pelvis

enters→femoral triangle
-on anteromedial aspect of thigh

with

• femoral a

• femoral v

• lymph nodes

Obturator Nerve Contributions+Innervations

contributions→l2-l4

innervation→all medial compartment muscles except pectineus+adductor magnus hamstring component

Obturator Nerve Exit+Enter

passes through pelvic cavity

exits→pelvis

enters→thigh via obturator foramen

Inferior Gluteal Nerve Contributions+Innervations

contributions→l5-s2

innervation→gluteus maximus

Inferior Gluteal Nerve Exit

exits→pelvis through greater sciatic foramen

Superior Gluteal Nerve Contributions+Innervations

contributions→l4-s1

innervations

• gluteus medius

• gluteus minimus

• tensor fasciae latae

Superior Gluteal Nerve Exit

exits→pelvis through greater sciatic foramen

Sciatic Nerve (General)

largest nerve in the body

composed of tibial n+common fibular n in one sheath

deep to piriformis in posterior view

divides into 2 major branches around popliteal fossa

• tibial n

• common fibular n

Sciatic Nerve Exit

Exits→pelvis via greater sciatic foramen

Sciatic Nerve Contributions+Innervations

contributions→l4-s3

innervations

• muscles in posterior compartment of thigh

• part of adductor magnus

• muscles in posterior compartment of leg

• muscles on sole of foot

Sciatica

pain in lower back+hip→radiates down back of thigh+back of leg to bottom of foot

causes

• herniated disc

• bone spurs compressing spinal nerves

Tibial Nerve (General)

branch of the sciatic n

found between calf muscles

at foot→divides into

• lateral plantar n

• medial plantar n

Tibial Nerve Contributions+Innervations

contributions→anterior divisions of l4-l3

innervations→supply intrinsic foot muscles

Tibial Nerve Exit+Enter

exits→posterior surface of tibia (between calf muscles)→wraps around medial malleolus

enters→foot→divides into medial+lateral plantar ns

Plantar Nerves

plantar surface of foot

divisions from tibial n

• medial plantar n

• lateral plantar n

Common Fibular Nerve (General)

branch of the sciatic n

found along top of fibula

divides into

• superficial fibular n

• deep fibular n

Common Fibular Nerve Contributions

contributions→l4-s2

Deep Fibular Nerve (General)

branch of the common fibular n

more anterior than superficial fibular n

Deep Fibular Nerve Exit+Enter

exits→runs along interosseous membrane between tibia+fibula

enters→dorsal surface of foot

Superficial Fibular Nerve (General)+Innervations

branch of the common fibular N

runs along the fibula

innervations

• foot plantarflexors

• skin of leg and foot

Sural Nerve (General)

superficial cutaneous branch of tibial n

between heads of gastrocnemius

Sural Nerve Exit+Enter

exits→down belly of gastrocnemius→goes around lateral malleolus

enters→foot

Sural Nerve Innervations

innervations

• skin on lower posterolateral surface of leg

• lateral side of foot

• digit 5

Lateral Sural Nerve (General)

branch off of common fibular n

can have communicating branch that connects to sural n (off tibial n)

Lateral Sural Nerve Innervations

innervation→skin over upper lateral leg

Sural Communicating Nerve

links sural n to lateral sural n

Sciatic Nerve Bony Landmarks

vertical line from highest point of iliac crest

line passing horizontally through first line midway between highest point of iliac crest+horizontal plane through ischial tuberosity

divides gluteal region into quadrants

• upper lateral quadrant

• upper medial quadrant

• lower medial quadrant

• lower lateral quadrant

Sciatic Nerve Visualization

passes through upper corner of lower medial quadrant→travels down lateral margin of lower medial quadrant

clinical→intramuscular injections

• given in anterior corner of upper lateral quadrant

• avoid sciatic+other vessels

Sensory Innervation of Anterior Leg

anteromedial aspect of thigh→obutrator n

anterior side of thigh (midline)→femoral n

anterolateral aspect of thigh→lateral cutaneous n of thigh from lumbar plexus

anteromedial aspect of lower leg→branch off femoral n

lateral side of lower leg (proximal)→branch off common fibular n

anteriolateral aspect of lower leg→branch off superficial fibular n

Sensory Innervation of Dorsal Foot

superficial fibular n

• dorsal surface of foot

• dorsal surfaces of digit 3+4

• dorsal surface of lateral half of digit 2

• dorsal surfaces of medial halves of hallus+digit 5 (no tips)

deep fibular n

• dorsal surface of lateral half of digit 1

• dorsal surface of medial half of digit 2

• dorsal surface of skin between digit 1+2 (no tips)

Sensory Innervation of Plantar Foot

sural n

• lateral 2/3 of plantar surface of foot
  -strip of skin!

tibial n

• plantar surface of calcaneus

medial plantar n

• plantar surface of medial half of digit 4

• plantar surfaces of digits 1-3

• medial plantar surface of foot

• anterior 2/3 plantar surface of foot

lateral plantar n

• plantar surface of digit 5

• plantar surface of lateral half of digit 4

• lateral portion of anterior 2/3 plantar surface

branch off femoral n

• medial strip

Sensory Innervation of Posterior Leg

sural n

• distal 1/3 posterolateral surface of lower leg

• midline strip

branch off tibial n→posterior calcaneal region

branch off common fibular n→proximal 2/3 posterolateral surface of lower leg