Posterior Leg Musculature

Question 1

Gastrocnemius

Answer 1

Origin:
- Medial head: just above the medial condyle of the femur
- Lateral head: lateral condyle of the femur
Insertion:
- Calcaneus
Action:
- Plantarflexes ankle
- Flexes knee
Nerve:
- Tibial portion of sciatic
- S1-2

Question 2

Soleus

Answer 2

Origin:
- Soleal line of tibia
- Upper fibula
Insertion:
- Calcaneus
Action:
- Plantarflexes ankle
Nerve:
- Tibial portion of sciatic
- S1-2

Question 3

Plantaris

Answer 3

Origin:
- Lateral femoral condyle
Insertion:
- Calcaneus
Action:
- Weakly plantarflexes ankle
- Weakly flexes knee
Nerve:
- Tibial portion of sciatic
- S1-2

Question 4

Popliteus

Answer 4

Origin:
- Lateral femoral epicondyle
Insertion:
- Soleal line of tibia
Action:
- Closed chain: laterally rotates femur on tibia & unlocks (flexes) knee
- Open chain: medially rotates tibia on femur & unlocks (flexes) knee
Nerve:
- Tibial portion of sciatic
- L5, S1

Question 5

Tibialis posterior

Answer 5

Origin:
- Posterior tibia
- Interosseous membrane
Insertion:
- Navicular tuberosity
- Plantar surface of cuneiforms & cuboid
- Bases of 2nd – 4th metatarsals
Action:
- Inverts & horizontally adducts foot
- Prevents hyperpronation while in gait
- Weakly plantarflexes ankle
Nerve:
- Tibial portion of sciatic
- L5, S1

Question 6

Flexor digitorum longus

Answer 6

Origin:
- Posterior surface of tibia
Insertion:
- Plantar surface of bases of 2nd-5th distal phalanges
Action:
- Primarily flexes 2nd-5th toes
- Weakly plantarflexes ankle
- Weakly inverts & adducts foot
Nerve:
- Tibial portion of sciatic
- L5, S1

Question 7

Flexor hallucis longus

Answer 7

Origin:
- Posterior, inferior 2/3 fibula
- Interosseous membrane
Insertion:
- Plantar surface of distal phalanx of hallux
Action:
- Flexes hallux
- Weakly plantarflexes ankle
- Weakly inverts & adducts foot
Nerve:
- Tibial portion of sciatic
- L5, S1