9-2. Posterior Compartment Overview

Question 1

What are the boundaries of the (entire) posterior compartment of the leg?

Answer 1

Anterior: posterior surface of tibia, interosseous membrane, posterior medial and posterior lateral surfaces of fibula, posterior intermuscular septum
Lateral/Posterior/Medial: deep fascia of the leg (crural fascia)

Question 2

What separates the deep and superficial posterior compartments of the leg?

Answer 2

Deep transverse intermuscular septum

Question 3

What are the general contents of the posterior muscular compartment?

Answer 3

• Knee flexors
• Ankle plantarflexors
• Foot invertors
• Digit plantarflexors

Question 4

What nerve innervates all of the muscles of the posterior compartment?

Answer 4

Tibial nerve*

**In SUPERFICIAL posterior compartment, the nerve segments are always S1,S2; in the DEEP posterior compartment the nerve segments vary.

Question 5

What are the proximal and distal attachments for Gastrocnemius?

Answer 5

Proximal:

• lateral head= lateral aspect of lateral femoral condyle
• medial head= superior to medial femoral condyle; popliteal surface of femur

Distal:
posterior surface of calcaneus via calcaneal/Achilles tendon

Question 6

What are the proximal and distal attachments for Soleus?

Answer 6

Proximal:

• Posterior head and superior 1/4 of posterior surface of fibula
• Soleal line and middle 1/3 of medial border of tibia
• tendinous arch between bony attachments

Distal:
posterior surface of calcaneus via calcaneal/Achilles tendon

Question 7

What are the proximal and distal attachments for Plantaris?

Answer 7

Proximal:

• Inferior end of lateral supracondylar line
• Oblique popliteal ligament

Distal:
Inserts on calcaneus medial to Achilles tendon or can join Achilles tendon

Question 8

What muscles are found in the superficial posterior compartment?

Answer 8

• Gastrocnemius
• Plantaris
• Soleus

Question 9

What muscles are found in the deep posterior compartment?

Answer 9

• Popliteus
• Flexor hallucis longus
• Flexor digitorum longus
• Tibialis posterior

Question 10

What actions does Gastrocnemius have?

Answer 10

• Flexes knee joint
• Plantarflexes ankle when knee is extended
• Contributes to inversion

Question 11

What actions does Soleus have?

Answer 11

• Plantarflexes ankle regardless of knee position

- Contributes to inversion

Question 12

What actions does Plantaris have?

Answer 12

• Weakly flexes knee

- Weakly plantarflexes ankle

Question 13

What muscles together are referred to as Triceps Surae?

Answer 13

Gastrocnemius and Soleus

Question 14

What are the notable differences between the two heads in Gastrocnemius?

Answer 14

• medial head tends to be larger than the lateral head

- the possible sesamoid/cartilage known as “fabella” is more commonly found in the lateral head

Question 15

Where is a Baker’s cyst usually found?

Answer 15

Between the medial head of gastrocnemius and the semi-membranosus tendon

Question 16

What is the clinical significance of a possible “accessory soleus” muscle?

Answer 16

Its distal belly is located medial to the calcaneal tendon–> its presence can cause tarsal tunnel syndrome

Question 17

What is the clinical significance of the plantaris muscle?

Answer 17

It is very small in humans and has a minor role–> can be removed and used for tendon grafts without any adverse effect on limb funciton

Question 18

What are the proximal and distal attachments for Popliteus?

Answer 18

Proximal:

• lateral surface of lateral femoral condyle
• lateral meniscus

Distal:
posterior surface of tibia, above soleal line

Question 19

What are the proximal and distal attachments for Flexor hallucis longus?

Answer 19

Proximal:

• inferior 2/3 of posterolateral surface of fibula
• inferior part of interosseous membrane
• *most lateral origin of the deep post. compartment muscles

Distal:
base of distal hallucal phalanx

Question 20

What are the proximal and distal attachments for Flexor digitorum longus?

Answer 20

Proximal:

• posterior surface of tibia inferior to soleal line
• by a broad tendon to fibula

Distal:
base of distal phalanges of lateral digits

Question 21

What are the proximal and distal attachments for Tibialis posterior?

Answer 21

Proximal:

• interosseous membrane
• posterior surface of tibia inferior to soleal line
• posteromedial surface of fibula

Distal:

• all tarsals, except talus
• bases of MT 2-4

Question 22

What is the segmental innervation of popliteus?

Answer 22

Tibial nerve (L4-S1)

Question 23

What is the segmental innervation of FHL?

Answer 23

Tibial nerve (S2, S3)

Question 24

What is the segmental innervation of FDL?

Answer 24

Tibial nerve (S2, S3)

Question 25

What is the segmental innervation of TP?

Answer 25

Tibial nerve (L4, L5)

Question 26

What actions does Popliteus have?

Answer 26

- weakly flexes knee and unlocks it by rotating femur 5* on a fixed tibia (closed chain kinetics) - medially rotates tibia on an unplanted limb (open chain kinetics)

Question 27

What actions does FHL have?

Answer 27

- plantarflexes hallux | - assists in inversion

Question 28

What actions does FDL have?

Answer 28

- plantarflexes lateral digits | - assists in inversion

Question 29

What actions does TP have?

Answer 29

- plantarflexes ankle | - inverts foot

Question 30

What is unique about popliteus in regards to its location?

Answer 30

It is the only posterior compartment muscle that does NOT cross the ankle

Question 31

How does popliteus contribute to stabilization of the knee?

Answer 31

When knee is partially flexed, popliteus may assist PCL in checking anterior displacement of femur on tibial plateau (ex- when walking downhill).

Question 32

What activity is happening in the posterior compartment during foot flat in the gait cycle?

Answer 32

Loading response: - eccentric contraction of triceps surae moderates ankle dorsiflexion - TP, FHL, FDL support the medial longitudinal arch as foot pronates

Question 33

What activity is happening in the posterior compartment during midstance in the gait cycle?

Answer 33

- triceps surae continues to control ankle dorsiflexion | - TP, FHL, FDL support restoration of medial longitudinal arch as foot begins to prepare for supination

Question 34

What activity is happening in the posterior compartment during terminal stance in the gait cycle?

Answer 34

- concentric contraction of triceps surae producing heel-up/heel-off - TP, FHL, FDL support medial longitudinal arch and stabilize forefoot for propulsion during toe-off

Question 35

At toe-off, where is the GRF line in relation to the ankle, knee, and hip?

Answer 35

Ankle: anterior Knee: posterior Hip: posterior

Question 36

Knowing where the GRF line is during toe-off, what muscle groups will be recruited at the hip/knee/ankle to offset the effect of the GRF and to keep body moving forward?

Answer 36

Ankle: plantarflexors Knee: extensors Hip: flexors

Question 37

Weakness of the ankle plantarflexors can result in insufficient propulsion. There is no toe-off, instead the entire foot will leave the ground at once. What is this compensatory gait?

Answer 37

Apropulsive/Calcaneal gait

Question 38

In apropulsive/calcaneal gait, what happens to the plantarflexors at midstance?

Answer 38

Plantarflexors will not be able to moderate the passive dorsiflexion that takes place at the ankle as body weight is transferred forward.

Question 39

How might a patient with an apropulsive/calcaneal gait try to compensate for the unmoderated passive dorsiflexion at the ankle as their body weight is transferred forward at midstance?

Answer 39

To counteract this ankle movement, the patient will often rotate the foot as far externally as possible to allow for push-off to occur at the midfoot.

Question 40

What structures form the tarsal tunnel?

Answer 40

Medial malleolus, calcaneal tuberosity, flexor retinaculum

Question 41

What are the contents of the tarsal tunnel?

Answer 41

Tom, Dick, (Very) And Very Nervous Harry - Tibialis Posterior - Flexor Digitorum Longus - Posterior Tibial Artery/Veins - Tibial Nerve - Flexor Hallucis Longus