10.3 Posterior Compartment of Leg

Question 1

What nerve are the muscles of the posterior compartment of the leg innervated by?
What is their function?

Answer 1

Tibial nerve

Plantar Flexion

Question 2

Identify the components of the Triceps surae
a.	Gastrocnemius
   (1)	Medial head
   (2)	Lateral head
b.	Soleus
Describe attachments and functions

Answer 2

Gastrocnemius

1. = fusiform, 2-headed muscle
2. Attachments:
   a. Lateral head: proximally, lateral aspect of lateral condyle; distally, posterior surface of calcaneus via calcaneal tendon
   b. Medial head: popliteal surface of femur above medial condyle; distally, posterior surface of calcaneus via calcaneal tendon
3. Actions: plantarflexes ankle when knee extended; raises heel while walking, flexes leg at knee

Soleus

1. Attachments:
   a. Proximally, posterior fibula and medial tibia; distally, posterior surface of calcaneus via calcaneal tendon
2. Actions: powerfully plantarflexes ankle, steadies leg on foot

Question 3

Identify the plantaris muscle, describe attachments, function, and innervation

Answer 3

1. Attachments:
   a. Proximally, supracondylar line on femur and oblique popliteal ligament; distally, posterior surface of calcaneus via calcaneal tendon
2. Actions: weakly assists in plantar flexion
3. Innervation: tibial nerve

Question 4

Identify the tendocalcaneous tendon

Answer 4

Achilles tendon: the distal attachment of the triceps surae to the calcaneus.

Question 5

Identify the flexor hallucis longus, attachments, and function

Answer 5

1. Attachments: Proximally, inferior posterior fibula and interosseus membrane; distally, base of distal phalanx of great toe
2. Actions: flexes great toe at all joints; weakly plantarflexes ankle, supports medial longitudinal arch of foot (important in toe-off)

Question 6

Identify the popliteus muscle, attachments, function, innervation

Answer 6

1. Attachments:
   a. Proximally, lateral surface of lateral femoral condyle and lateral meniscus; Distally, posterior tibia
2. Actions: weakly flexes knee and medially rotates tibia on femur (or vice versa)
   Tibial nerve inneravtion

Question 7

Identify the flexor digitorum longus, attachments, and function, and innervation

Answer 7

1. Attachments: Proximally, medial posterior tibia, fibula; distally, base of distal phalanges of lateral 4 digits
2. Actions: flexes lateral 4 digits, plantarflexes ankle, supports longitudinal arches
   Tibial nerve innervated (posterior leg)

Question 8

Identify the tibialis posterior, attachments/function, and innervation.

Answer 8

1. Attachments: Proximally, interrosseus membrane, posterior tibia and fibula; distally, to navicular tuberosity, cuneiforms, cuboid, and base of MTs 2-4
2. Actions: plantarflexes ankle, inverts foot, supports medial longitudinal arch of foot during weight bearing (mainly this function – so important in stance phase)
   Tibial nerve innervated (posterior leg).

Question 9

Identify the tibial nerve and its divisions

Answer 9

– divides into medial and lateral plantar nerves posteroinferior to medial malleolus

Question 10

Identify the Sural nerve and its divisions

Answer 10

usually formed by medial sural cutaneous n. (from tibial n.) and sual communicating branch of common fibular n.

Question 11

Identify the posterior tibial artery and its branches

Answer 11

3. Posterior tibial a. – blood supply to posterior compartment of leg and foot (from popliteal a.)
   a. Fibular a.
   b. Medial plantar a.
   c. Lateral plantar a.