17. Anterior, lateral and posterior compartments of the leg

Question 1

What are the 4 muscles in the anterior compartment of the leg?

Answer 1

tibialis anterior, extensor digitorum longus, extensor hallucis longus, peroneus/ fibularis tertius

Question 2

What do the anterior muscles of the leg act to do?

Answer 2

• dorsiflexion and inversion of foot at ankle joint

- extensor digitorum longus and extensor hallucis longus muscles also extend the toes

Question 3

What are the muscles in the anterior compartment of the leg innervated by?

Answer 3

deep peroneal/ fibular nerve (L4-L5)

Question 4

What is the blood supply to the anterior compartment of the leg?

Answer 4

anterior tibial artery

Question 5

Describe the muscle: tibialis anterior

• origin
• insertion
• actions
• innervation

Answer 5

• originates from the lateral surface of the tibia
• tendon passes deep to the extensor retinacula at the ankle and inserts onto the medial cuneiform and the base of the first metatarsal
• strongest dorsiflexor, also inverts foot
• innervated by deep peroneal (fibular) nerve

Question 6

How can the strength of the tibialis anterior be tested?

Answer 6

Patient asked to stand on heels with forefeet raised

Question 7

Describe the muscle: extensor digitorum longus

• origin
• insertion
• actions
• innervation

Answer 7

• originates from the lateral condyle of tibia, the medial surface of the fibula and the interosseous membrane
• fibres converge into a single tendon which passes deep to the extensor retinacula of the ankle then divides into four tendons on dorsum of the foot
• tendons insert onto the middle and distal phalanges of the second to fifth toes
• actions to extend the lateral four toes and assists in dorsiflexion
• innervated by deep fibular nerve

Question 8

Describe the muscle: extensor Hallucis longus

• origin
• insertion
• actions
• innervation

Answer 8

• originates from medial surface of fibular shaft
• tendon crosses anterior to the ankle joint, beneath the extensor retinacula
• attaches to the base of the distal phalanx of the great toe
• acts to extend great toe and assists dorsiflexion
• innervated by deep fibular nerve

Question 9

Where does the extensor digitorum longus muscle lie?

Answer 9

lies lateral and deep to the tibialis anterior muscle

Question 10

The tendons of which muscle on the dorsum of the foot can be palpated?

Answer 10

The tendons of the EDL can be palpated on the dorsum of the foot.

Question 11

Where is the extensor Hallucis longus muscle located?

Answer 11

located deep to the extensor digitorum longus and tibialis anterior

Question 12

Describe the muscle: peroneus/ fibularis tertius

• origin
• insertion
• actions
• innervation

Answer 12

• originate from the medial surface of fibula, inferior to the origin of the EDL
• descends with EDL, beneath the extensor retinacula, until they reach the dorsal surface of the foot
• tendon then diverges from EDL and inserts onto the base of the fifth metatarsal
• assists eversion and dorsiflexion
• innervated by deep fibular nerve

Question 13

What does the lateral compartment of the leg consist of?

Answer 13

There are two muscles in the lateral compartment of the leg: the peroneus (fibularis) longus and peroneus (fibularis) brevis

Question 14

What do the muscles of the lateral leg do?

Answer 14

• evert the foot

* stabilise the medial margin of the foot during running and prevent excessive inversion

Question 15

What are the muscles in the lateral compartment of the leg innervated by?

Answer 15

superficial peroneal (fibular) nerve

Question 16

Describe the muscle: peroneus (fibularis) longus

• origin
• insertion
• actions
• innervation

Answer 16

• originates from the upper lateral surface of the fibula and the lateral tibial condyle
• the fibres converge into a tendon which descends into the foot, posterior to the lateral malleolus
• the tendon crosses under the midfoot and inserts onto the plantar surface at the medial cuneiform and base of the first metatarsal
• acts to evert and assist plantarflexion. Also supports the medial and transverse arches of the foot
• innvervated by the superficial fibular (peroneal) nerve

Question 17

Compare peroneus (fibularis) longus to peroneus (fibularis) brevis

Answer 17

Peroneus (fibularis) longus is the larger and more superficial muscle within the lateral compartment.
The peroneus (fibularis) brevis muscle is deeper and shorter than the peroneus (fibularis) longus

Question 18

Describe the muscle: peroneus (fibularis) brevis

• origin
• insertion
• actions
• innervation

Answer 18

• originates from the inferolateral surface of the fibular shaft
• the tendon descends with the tendon of the peroneus longus into the foot
• the peroneus brevis tendon passes posterior to the lateral malleolus where it lies deep to the tendon of the peroneus longus
• inserts onto a tubercle on the base of the fifth metatarsal
• everts foot and supports lateral longitudinal arch
• innervated by Superficial fibular (peroneal) nerve, L4-S1.

Question 19

What does the posterior compartment of the leg consist of?

Answer 19

7 muscles or organised into: the superficial posterior compartment and the deep posterior compartment which are separated by fascia

Question 20

What are the functions of muscles in the posterior compartments of the leg?

Answer 20

Plantarflexion and inversion of the foot

Question 21

What are the muscles in the posterior compartments of the leg innervated by?

Answer 21

The tibial nerve, a terminal branch of the sciatic nerve

Question 22

What do the muscles of the superficial compartment of the posterior leg all insert into?

Answer 22

The calcaneus via the calcaneal (Achilles) tendon

Question 23

What are the two bursae associated with the calcaneal tendon and what is their function?

Answer 23

• subcutaneous - between skin and the tendon
• deep - between the tendon and the calcaneus

minimise friction during movement

Question 24

What are the muscles in the superficial posterior compartment of the leg?

Answer 24

gastrocnemius, soleus, plantaris

Question 25

Describe the muscle: gastrocnemius - origin - insertion - actions - innervation

Answer 25

• most superficial • lateral head originates from the lateral femoral condyle, and the medial head from the medial femoral condyle • inserts onto calcaneal tuberosity • plantarflexion at the ankle joint and as it crosses the knee joint, aids in knee flexion - innervated by tibial nerve

Question 26

What is formed when the gastrocnemius fibres converge?

Answer 26

fibres converge and form a single tendon which combines with the tendons of the soleus and plantaris to form the calcaneal tendon

Question 27

Describe the muscle: plantaris - origin - insertion - actions - innervation

Answer 27

• small muscle with a long thin tendon • originates from the lateral supracondylar line of the femur • descends medially, condensing into a tendon that runs down the leg, between the gastrocnemius and soleus • the tendon blends with these muscles in the calcaneal tendon • weak plantarflexor at ankle joint and weak knee flexor - innervated by tibial nerve

Question 28

Why can the plantaris be harvested by plastic surgeons for reconstructive surgery elsewhere?

Answer 28

Very weak plantarflexor and knee flexor - not functionally important Absent in 10% of people anyway

Question 29

Describe the muscle: soleus - origin - insertion - actions - innervation

Answer 29

* located deep to the gastrocnemius and plantaris muscles * large and flat * originates from the soleal line of the tibia and the proximal fibula * inserts inferiorly with the gastrocnemius and plantaris, via the calcaneal tendon, onto the calcaneal tuberosity * plantarflexion at ankle joint * innervated by tibial nerve

Question 30

What muscles are in the deep posterior compartment?

Answer 30

flexor digitorum longus, tibialis posterior, flexor hallucis longus which all act on the ankle and foot, and the popliteus (acts only on knee joint)

Question 31

Describe the muscle: popliteus - origin - insertion - actions - innervation

Answer 31

* most superior * posterior to knee joint, forms part of the floor of the popliteal fossa * originates from the tibia proximal to the soleal line from which it passes superolaterally to insert onto the lateral condyle of the femur and the posterior horn of the lateral meniscus * laterally rotates the femur on the tibia, unlocking the knee joint so flexion can occur * innervated by tibial nerve

Question 32

Describe the muscle: tibialis posterior - origin - insertion - actions - innervation

Answer 32

• deepest • lies between the flexor digitorum longus and flexor hallucis longus • originates from the interosseous membrane between the tibia and fibular and from the posterior surfaces of the two bones • the tendon enters the sole of the foot by passing posterior to the medial malleolus and inserts onto the plantar surface of the navicular and medial cuneiform bones • inverts and plantarflexes the foot and maintains medial arch - innervated by the tibial nerve

Question 33

Describe the muscle: flexor digitorum longus - origin - insertion - actions - innervation

Answer 33

• smaller than flexor hallucis longus • located medially in deep posterior leg compartment • originates from medial surface of the tibia and enters the sole of the foot by passing posterior to the medial malleolus • in the sole it crosses superficial to the flexor hallucis longus tendon then divides into four tendons that insert onto the base of the distal phalanx of each of the lateral four digits • flexes lateral four toes and assists in plantar flexion of ankle and inversion of midfoot - innervated by tibial nerve

Question 34

Describe the muscle: flexor hallucis longus - origin - insertion - actions - innervation

Answer 34

• lateral side of the deep posterior compartment of the leg • originates from the posterior surface of the fibula, passes posterior to the medial malleolus and inserts onto the plantar surface of the base of the distal phalanx of the great toe • flexes great toe and assists in plantarflexion of the ankle and inversion of the mid foot • innervated by tibial nerve

Question 35

Which tendons of the posterior compartments of the leg act on what parts of the foot and ankle?

Answer 35

* tibialis posterior: plantar surfaces of the navicular and medial cuneiform bones * flexor digitorum longus: base of the distal phalanx of each of the lateral four digits * flexor hallucis longus: base of the distal phalanx of the great toe

Question 36

The arrangement of the tendon insertions in the pes anserinus (Goose’s foot) at the anteromedial surface of the proximal tibia (from anterior to posterior) can be remembered by?

Answer 36

Say Grace before Tea = Sartorius, gracilis, semitendinosus

Question 37

The arrangement of the structures posterior to the medial malleolus of the ankle (anterior to posterior) can be remebered by?

Answer 37

``` “Tom, Dick, And Very Nervous Harry”:  Tibialis posterior  flexor Digitorum longus tendon  posterior tibial Artery  posterior tibial Vein (as venae comitantes of artery)  tibial Nerve  flexor Hallucis longus ```

Question 38

The mnemonics for recalling the actions of the muscles supplied by the common peroneal and tibial nerves are?

Answer 38

PED: Common Peroneal Everts and Dorsiflexes (injury = foot drop) TIP: Tibial Inverts and Plantar flexes (injury = can’t walk on TIP toes)