Posterior Leg

Question 1

Describe the popliteal fossa boundaries.

Answer 1

diamond-shaped space behind knee.

Bounded by:
Biceps femoris
Semimembranosus 
Gastrocnemius – medial head
Gastrocnemius – lateral head

Question 2

What does the popliteal fossa contain?

Answer 2

Contains the tibial and common fibular nerves, popliteal artery and vein, genicular arteries, and the articular branch of the obturator nerve.

Contents (superficial to deep): (tibial n, popliteal v, popliteal a)
small saphenous vein, tibial and common fibular nerves, popliteal vein, popliteal artery, articular branch of obturator nerve, lymph nodes/fat, knee.

Question 3

Describe the common fibular nerve.

Answer 3

follows medial border of biceps laterally. Proprioceptive branches follow genicular arteries. Divides into 2 branches as it leaves the fossa. Deep Fibular enters anterior compartment of leg, while the Superficial Fibular enters lateral compartment of leg.

Question 4

What are the most powerful flexors?

Answer 4

hamstring muscles…
semimembranosus
semitendinosus
biceps femoris

Question 5

Describe the fascial compartments of the leg.

Answer 5

anterior: dorsiflexion of foot and extension of toes (deep fibular n.)
lateral: eversion of foot (superficial fibular n)
posterior: plantar flexion and inversion of foot, flexion of toes (tibial nerve)

Question 6

Describe the popliteal artery.

Answer 6

Popliteal Artery: continuation of femoral a.; gives off anastamotic branches around knee:
Superior medial and lateral genicular aa.
Inferior medial and lateral genicular aa.

Divides at distal end of popliteal fossa into anterior and posterior tibial arteries. (and fibular artery)

Question 7

Describe the anterior leg muscles. What innervates them?

Answer 7

All muscles innervated by deep fibular nerve. all muscles dorsiflex the foot.

tibialis anterior- dorsiflex and invert foot
extensor digitorum longus- extends toes (dorsiflex foot)
extensor hallucis longus- extends big toe (dorsiflex foot)
fibularis tertius- dorsiflex and evert foot

(fibularis=peroneus)

Question 8

What can overuse of anterior leg muscles cause?

What holds extensor tendons in place?

Answer 8

Overuse of muscles (TA) can cause separation from periosteum, leading to pain and “shin splints”

Superior and Inferior extensor retinacula hold extensor tendons in place and prevent “bowstringing.” Inferior retinaculum is Y shaped with the stem attaching to the lateral side of the calcaneus. The upper arm is attached to the medial malleolus, while the lower arm attaches to the first cuneiform on the sole of the foot.

Question 9

When does foot drop occur?

Answer 9

Foot drop results if the tibialis anterior muscle is paralyzed due to injury to the common or deep fibular nerves.

(no dorsiflexion, foot drop)

Question 10

Describe the lateral leg muscles. What is their function? What innervates them?

Answer 10

superficial fibular nerve

function to EVERT to the foot

fibularis longus
fibularis brevis

Question 11

Describe the posterior tibial artery.

Answer 11

direct continuation of the popliteal artery. It descends inferiorly over the tibialis posterior m. and deep to the gastrocnemius and soleus mm, then courses medially between the flexor digitorum longus and flexor hallucis longus mm. It passes posterior to the medial malleolus (w/vein).

Question 12

Describe fibular (peroneal) artery.

Answer 12

arises from the posterior tibial a. distal to the tibialis posterior m, then courses laterally in a fibrous canal between the tibialis posterior and flexor hallucis longus mm, and runs deep to the FHL. It gives branches to the lateral malleolus.

Question 13

Describe the anterior tibial artery.

Answer 13

branches from the popliteal artery just below the popliteus m, and passes between the 2 heads of the tibialis posterior and between the tibia and fibula above the interosseus membrane to the anterior compartment of the leg. It is joined by the deep fibular n. After crossing into the anterior compartment, the artery lies deep to the tibialis anterior m along with the deep fibular n. It lies medial to the extensor digitorum longus and extensor hallucis longus mm.

After passing beneath the superior extensor retinaculum, it gives off medial and lateral malleolar branches, then passes below the inferior extensor retinacula, where it becomes the dorsalis pedis a.

Question 14

Describe the nerves of the anterior and lateral leg.

Answer 14

Superficial Fibular Nerve (L4-S2, lateral compartment): after branching from the common fibular n. at the neck of the fibula, it innervates the lateral compartment muscles (FL, FB). It leaves mid-leg to become cutaneous in the lateral leg and dorsum of the foot.

Deep Fibular Nerve (L4-S2, anterior compartment): enters and innervates anterior leg compartment muscles (EDL, EHL, TA, FT). It continues inferiorly deep to the extensor retinacula to innervate EDB & EHB, and terminates as a cutaneous branch between the hallux (big toe) and second toe.

Saphenous Nerve (L3-4): cutaneous branch on medial side of leg and ankle

Question 15

Describe the superficial muscles of the posterior leg.

Answer 15

(Tibial n.)

Gastrocnemius: 2 heads originating from femur (medial & lateral condyles); flexes leg and plantar flexes foot (functions best with full leg extension & slight dorsiflexion of ankle); strength muscle

Plantaris: originates proximal to knee from lateral supracondylar line; joins calcaneal tendon superficial to soleus and deep to gastrocnemius; tendon nicknamed ”freshman nerve”

Soleus: originates distal to knee, so functions only to plantar flex foot; postural muscle

superficial muscles all join to achiles tendon to insert in calcaneous

Question 16

Describe the deep muscles of the posterior leg.

Answer 16

(Tibal n. and post tibial artery)
Tom Dick And Nervous Harry

Popliteus: inferior portion of floor of popliteal fossa; flexes and medially rotates leg; helps “unlock” fully extended knee

Tibialis posterior: plantar flexion of ankle, adducts and inverts foot; supports medial longitudinal arch as it passes under tarsal bones

Flexor digitorum longus: inserts onto distal phalanges of toes 2-5 (similar to arm); crosses superficially over tibialis posterior tendon at medial malleolus; passes superficially over flexor hallucis longus tendon in foot

Flexor hallucis longus: also inserts onto distal phalanx of 1st toe; powerful flexion to 1st toe during walking (push off); plantar flex & invert foot also

Question 17

Describe the flexor retinaculum.

Answer 17

Flexor Retinaculum: Extends from the tip of the medial malleolus to the medial process of the calcaneous; binds tibialis posterior, flexor digitorum longus, and flexor hallucis longus mm.

Question 18

Tom, Dick And Nervous Harry

Answer 18

Tom, Dick And Nervous Harry pass distal to the medial malleolus (medial to lateral from big toe)

Tibialis posterior tendon 
flexor Digitorum longus tendon 
posterior tibial Artery
tibial Nerve
flexor Hallucis longus tendon.

Question 19

What are the nerves of the posterior leg?

Answer 19

common fibular nerve

tibial nerve

Question 20

Describe the tibial nerve.

Answer 20

Tibial Nerve (L4-S3): branches from sciatic above popliteal fossa. It innervates gastrocnemius, soleus, plantaris and popliteus mm., and gives off medial sural cutaneous n. and proprioceptive branches to knee. It courses deep to the soleus m., and innervates deep compartment muscles (tibialis posterior, flexor digitorum longus, flexor hallucis longus). It passes posteriorly to the medial malleolus and divides into medial and lateral plantar nerves in the foot.

Question 21

Describe the common fibular nerve

Answer 21

Common Fibular Nerve (L4-S2): branches from sciatic above popliteal fossa. It provides proprioceptive branches to the knee and gives off the lateral sural cutaneous n. (which joins the medial sural cutaneous to form the sural nerve). It passes along the posterior edge of the biceps femoris m. and enters the lateral compartment of the leg, and divides at the neck of the fibula deep to fibularis longus m. into the superficial and deep fibular nerves.

Deep Fibular enters anterior compartment of leg (tibialis anterior, extensor hallucis longus, extensor digitorum longus, fibularis tertius);

Superficial Fibular enters lateral compartment of leg (fibularis longus and brevis).

Question 22

Describe the nerves of the dorsum of the foot.

Answer 22

Superficial Fibular Nerve: cutaneous to most of the dorsum of the foot except tips of toes.

Deep Fibular Nerve: 2 muscles (EHB, EDB) and sensory between 1st & 2nd toes.

Question 23

Describe the dermatomes of the foot.

Answer 23

tip of first 3 toes and half of 4th - medial plantar
tip of half fourth and fifth toe- lateral plantar nerve
between big toe and first toe- deep fibular nerve
toes lateral ankle- superficial fibular
lateral side of foot- sural nerve
medial ankle and part of foot- saphenous nerve