Common Fibular Nerve

Question 1

What are the nerve roots of the common fibular nerve?

Answer 1

L4-S3

Question 2

What are the motor functions of the common fibular nerve?

Answer 2

Innervates the short head of the biceps femoris directly

Supplies, via branches, the muscles in the lateral and anterior compartments of the leg

Question 3

What are the sensory functions of the common fibular nerve?

Answer 3

Innervates the skin over the upper lateral and lower posterolateral leg
Supplies (via branches) cutaneous innervation to the skin of the anterolateral leg, and the dorsum of the foot

Question 4

Where does the common fibular nerve begin?

Answer 4

At the apex of the popliteal fossa, where the sciatic nerve bifurcates into the tibial and common fibular nerves

Question 5

What is the anatomical course of the common fibular nerve?

Answer 5

It follows the medial border of the biceps femoris, running in a lateral and inferior direction, over the lateral head of the gastrocnemius.

Question 6

What happens as the common fibular nerve passes over the lateral head of the gastocnemius?

Answer 6

It gives rise to two cutaneous branches, which contribute to the innervation of the skin of the leg

Question 7

How does the common fibular nerve enter the lateral compartment of the leg?

Answer 7

The nerve wraps around the neck of the fibula, passing between the attachments of the fibularis longus muscle

Question 8

Where does the common fibular nerve terminate?

Answer 8

When it passes between the attachments of the fibularis longus muscle

Question 9

How does the common fibular nerve terminate?

Answer 9

By dividing into the superficial fibular and deep fibular nerves

Question 10

What muscle does the common fibular nerve innervate?

Answer 10

The short head of the biceps femoris

Question 11

What is the biceps femoris muscle part of?

Answer 11

The hamstring muscles

Question 12

What do the hamstring muscles do?

Answer 12

Flex at the knee

Question 13

What muscles does the superficial fibular nerve innervate?

Answer 13

The muscles of the lateral compartment of the leg- fibularis longus and brevis

Question 14

What do the muscles of the lateral compartment of the leg do?

Answer 14

Act to evert the foot

Question 15

What muscles does the deep fibular nerve innervate?

Answer 15

The muscles of the anterior compartment of the leg- the tibialis anterior, extensor digitorum longus and extensor hallucius longus
Some intrinsic muscles of the foot

Question 16

What do the muscles of the anterior compartment of the leg do?

Answer 16

Act to dorsiflex the foot, and extend the digits

Question 17

What happens if the common fibular nerve is damaged?

Answer 17

The patient may lose the ability to dorsiflex and evert the foot and extend the digits

Question 18

What cutaneous branches arise directly from the common fibular nerve?

Answer 18

Sural communicating nerve

Lateral sural cutaneous nerve

Question 19

Where to the cutaneous branches of the common fibular nerve arise?

Answer 19

Just as it moves over the lateral head of the gastrocnemius

Question 20

What does the sural communicating nerve combine with?

Answer 20

A branch of the tibial nerve to form the sural nerve

Question 21

What does the sural nerve do?

Answer 21

Innervates the skin over the posterolateral leg

Question 22

What does the lateral sural cutaneous nerve?

Answer 22

Innervates the skin over the upper lateral leg

Question 23

What is the sensory function of the superficial fibular nerve?

Answer 23

Innervates the skin of the anterolateral leg, and dorsum of the foot (except the skin between the first and second toes)

Question 24

What is the sensory function of the deep fibular nerve?

Answer 24

Innervates the skin between the first and second toes

Question 25

How is the common fibular nerve most commonly damaged?

Answer 25

By a fracture of the fibula, or use of a tight plaster cast

Question 26

What can any fractures of the fibular cause?

Answer 26

Nerve palsy

Question 27

Why can any fractures of the fibular cause nerve palsy?

Answer 27

Because the anatomical course of the common fibular nerve causes it to wrap round the neck of the fibula

Question 28

What will happen in patients with common fibular nerve damage?

Answer 28

They will lose the ability to dorsiflex the foot at the ankle joint, and hence the foot will appear plantarflexed- known as footdrop
May present with a characteristic gait, as a result of the footdrop
Loss of sensation over the dorsum of the foot, and the lateral side of the leg

Question 29

Why is innervation preserved on the medial side of the leg in common fibular damage?

Answer 29

By the saphenous nerve, a branch of the femoral

Question 30

Why is innervation preserved on the heel and sole in common fibular nerve damage?

Answer 30

Supplied by the tibial nerve, a branch of the sciatic