Posterior Compartment of the Leg (Back of Leg)

Question 1

State two nerves that supply the skin of the lateral one third of the posterior leg and state their root values.

Answer 1

1. Lateral cutaneous sural nerve: L4, 5, S1
2. Sural communicating nerve: L5, S1, 2
3. [Diagram]

Question 2

State two nerves that supply the skin of the middle one third of the posterior leg and state their root values.

Answer 2

1. Sural nerve (L5, S1, 2)
2. Posterior cutaneous nerve of thigh (S1, 2, 3)
3. [Diagram]

Question 3

State two nerves that supply the skin of the medial one third of the posterior leg and state their root values.

Answer 3

1. Saphenous nerve (L3, 4)
2. Posterior division of the medial cutaneous nerve of the thigh (L2, 3)

Question 4

Identify the nerve that supplies the skin of the heel and the adjoining medial side of the sole of the foot.

Answer 4

medial calcaneal branch of the tibial nerve

Question 5

State the attachments of the flexor retinaculum.

Answer 5

Superiorly: posterior border and tip of the medial malleolus

Inferiorly: medial process of the calcaneal tuberosity

Question 6

Name all the structures that pass deep to the flexor retinaculum in order from medial to lateral.

Answer 6

1. Tendon of tibialis posterior
2. Tendon of flexor digitorum longus
3. Posterior tibial artery and its branches
4. Posterior tibial nerve and its terminal branches
5. Tendon of flexor hallucis longus

“The Doctors Are Not Here”

Note:
Some authorities refer to the deep peroneal nerve as anterior tibial nerve.

Question 7

Describe the boundaries of the posterior compartment of the leg.

Answer 7

Anteriorly: posterior surfaces of the tibia, fibula, interosseous membrane, and posterior intermuscular septum [there’s no medial and lateral intermuscular septae!]

Posteriorly: Deep fascia of the leg extending from the medial border of the tibia to the posterior intermuscular septum

[Diagram]

Question 8

Describe the attachments of the deep transverse septum of the posterior compartment of the leg.

Answer 8

Medially: proximal part of the soleal line and vertical ridge on the posterior surface of the tibia
Laterally: medial crest of the fibula

Question 9

Describe the origin of gastrocnemius muscle.

Answer 9

Medial head: popliteal surface of the femur and adjoining posterosuperior aspect of the medial condyle of the femur
Lateral head: lateral surface of the lateral condyle of the femur
[Diagram: map of origin and insertions of leg muscles]

Question 10

State the insertion of gastrocnemius.

Answer 10

The tendon of this muscle fuses with the tendon of the soleus to form the tendo calcaneus or tendo-Achilles, which is inserted into the middle third of the posterior aspect of the calcaneus.

Question 11

Describe the origin of soleus.

Answer 11

1) back of the head and upper fourth of the posterior surface of the shaft of the fibula
2) soleal line and middle third of the medial border of the shaft of tibia
3) tendinous soleal arch between tibia and fibula

Question 12

State the insertion of soleus.

Answer 12

Its tendon fuses with the tendon of gastrocnemius, which inserts on the posterior aspect of the calcaneus.

Question 13

Name the sesamoid bone that may be found in the tendon of origin of the lateral head of gastrocnemius.

Answer 13

Fabella

Question 14

State two actions of gastrocnemius.

Answer 14

1. Plantar flexion of the ankle when the knee is extended
2. Flexion of the leg at the knee joint

Question 15

State the nerve that supplies gastrocnemius, soleus and plantaris and give its root values.

Answer 15

Tibial nerve (anterior rami of S1, S2)

Question 16

State two actions of soleus.

Answer 16

1. Plantar flexion of the ankle independent of the position of the knee
2. Steadies the leg on the foot during standing

Question 17

Describe the origin of plantaris (2).

Answer 17

1. Lower part of the lateral supracondylar line of the femur
2. Oblique popliteal ligament
3. [Diagram: plantaris]
4. [Diagram: osteology of the femur]

Question 18

Describe the insertion of plantaris.

Answer 18

Its thin and long tendon inserts medial to the tendocalcaneus on the posterior aspect of the calcaneus. [Diagram]

Question 19

Which muscle’s tendon is referred to as the Freshman’s nerve? Why is it reffered to in this way?

Answer 19

Plantaris muscle.
Reason: Its long, thin tendon is often mistaken for a nerve by first-year medical students during dissection. The plantaris muscle is a small muscle with a short belly and a long slender tendon.
[Cadaveric image]

Question 20

Why is soleus called the peripheral heart?

Answer 20

There are large valveless venous sinuses within its mass. When it contracts, the blood in these sinuses is pumped upwards. When it relaxes, it sucks the blood from the superficial veins through the perforators.

Question 21

What is the soleal arch, and what is its importance?

Answer 21

The soleal arch, also known as the tendinous arch of the soleus muscle, is a structure in the lower leg, formed by some fibers of the soleus muscle that arise from a tendinous arch placed between the tibial and fibular origins of the muscle.
IMPORTANCE: This arch spans over and protects the popliteal vessels and the tibial nerve as they run in front of it.

Question 22

State one action of plantaris.

Answer 22

Very weak plantar flexion of the ankle

Question 23

Describe the origin of popliteus.

Answer 23

1. It has an intracapsular origin from the lateral aspect of the lateral condyle of the femur (popliteal groove of femur)
2. Outer margin of the lateral meniscus of the knee joint
3. [Cadaveric image 1] [Cadaveric image 2]

Question 24

State the insertion of popliteus.

Answer 24

medial 2/3 of the posterior surface of the shaft of the tibia above the soleal line

Question 25

State the action of the popliteus.

Answer 25

It unlocks the fully extended (locked) knee joint by rotating the femur laterally in the initial stages of flexion of the knee.

Question 26

State the pattern of blood supply to gastrocnemius.

Answer 26

end artery pattern, from sural artery

NB: It is one of the rare muscles that get their blood supply from only one artery, the sural artery, which is a branch of the popliteal artery. The sural arteries are terminal arteries, meaning that their blockage or occlusion would result in necrosis of the corresponding muscle tissue.

Further notes:
The Sural Arteries, also known as the inferior muscular arteries, are typically two large branches that arise from the distal part of the popliteal artery. These arteries descend ventrally to the triceps surae muscle. They are distributed to the gastrocnemius, soleus, and plantaris muscles.

Question 27

Tibialis posterior
(a) action
(b) innervation
(c) origin
(d) insertion

Answer 27

(a) action: (1) inverter of the foot, (2) it supports the medial longitudinal arch of the foot

(b) innervation: tibial nerve (anterior rami of L4 and L5)

(c) origin
✓ upper two thirds of the lateral part of the posterior surface of the tibia below the soleal line
✓ upper two third of the posterior surface of the interosseous membrane
✓ upper two-thirds of the posterior surface of the fibula

(d) insertion
✓ tuberosity of the navicular bone
✓ slips pass to all tarsals, except talus, and bases of 2nd to 4th metatarsals

[Diagram]

Question 28

The fibular artery is a branch of the _____________ artery.

Answer 28

posterior tibial artery
[Diagram]

Question 29

The sural nerve is formed from the union of two cutaneous nerves. Name them and state the nerves from which they branch.

Answer 29

1. Medial sural cutaneous nerve, a branch of the tibial nerve
2. Sural communicating nerve, a branch of the lateral sural cutaneous nerve
3. [Diagram]

Question 30

Describe the boundaries of the tarsal tunnel.

Answer 30

Floor: concave surface formed by medial aspect of tibia, talus and calcaneus
Roof: flexor retinaculum
[Diagram]

Question 31

State two functions of sesamoid bones (2 marks)

Answer 31

● Reduce friction
● Straighten pull of muscles
● Increase mechanical advantage
● Reduce wearing out of tendons

Question 32

[3-minute video]: the Posterior Tibial artery

Answer 32

🙂