Muscles - Leg (Posterior Compartment) Flashcards
Tibialis posterior
Deepest of the four muscles. It lies between the flexor digitorum longus and flexor hallucis longus.
Origin - interosseous membrane; posterior surface of tibia and fibula.
Insertion - enters the foot posterior to medial malleolus and attaches to the plantar surfaces of the medial tarsal bones.
Innervation - tibial nerve.
Actions - inverts and plantarflexes the. Maintains the medial arch of the foot.
Soleus
Located deep to the gastrocnemius. Large and flat, like a sole fish.
Origin - soleal line of tibia and proximal fibular area.
Insertion - narrows down as it descends the leg and joins the calcaneal tendon.
Innervation - tibial nerve
Actions - plantarflexes the foot at the ankle
What are the deep muscles of the posterior compartment?
1) Popliteus
2) Tibialis posterior
3) Flexor digitorum longus
4) Flexor hallucis longus
These act only on the knee joint.
What nerve innervates the muscles of the posterior compartment?
The tibial nerve, a terminal branch of the sciatic nerve.
Clinical relevance - ruptured calcaneal tendon
Rupture of the calcaneal tendon refers to a partial or full tear of the tendon. It is more likely to occur in people with a history of calcaneal tendonitis.
This is injury is usually sustained during forceful plantar flexion. The patient will be unable to plantarflex the foot during resistance. The affected foot will remain permanently dorsiflexed. The soleus and the gastrocnemius can contract to form a lump in the calf region.
Treatment is usually non-surgical, except in those with active lifestyles.
Gastrocnemius
Origin (lateral head) - lateral femoral condyle
Origin (medial head) - medial femoral condyle
Insertion - fibres converge to form a single muscle belly - in the lower part of the leg, the gastrocnemius combines with the soleus to form the calcaneal tendon, which inserts onto the calcaneus bone.
Innervation - tibial nerve
Actions - plantarflexes at the ankle joint, and because it crosses at the knee, it flexes there.
How many muscles are there in the posterior compartment?
7 muscles - subdivided into superficial and deep muscles.
Flexor digitorum longus
Smaller than the flexor hallucis longus. located medially in the posterior leg.
Origin - medial surface of tibia.
Insertion - attaches to the plantar surface of the lateral four digits.
Innervation - tibial nerve
Actions - flexes the lateral four toes.
Popliteus
The popliteus is located superiorly in the leg. It lies behind the knee joint, forming the base of the popliteal fossa.
Origin - lateral condyle of femur and posterior horn of the lateral meniscus.
Insertion - it then runs inferomedially towards the tibia, and inserts just above the soleal line.
Innervation - tibial nerve
Actions - laterally rotates the femur on the tibia - ‘unlocking’ the knee joint so that flexion can occur.
What are the superficial muscles of the leg?
What tendon do they ultimately form?
1) Gastrocnemius
2) Plantaris
3) Soleus
These muscles form the characterisc ‘calf’ shape of the posterior leg.
They all insert into the calcaneus, via the calcaneal tendon (achilles tendon).
Calcaneal reflex tests S1-S2 roots.
Plantaris
Located deep to the gastronemius. It is large and flat, like a fish.
Origin - lateral supracondylar line of the femur.
Insertion - descends medially - condensing into a tendon that runs down the leg, between the gastrocnemius and the soleus. The tendon blends in with the calcaneal tendon.
Innervation - tibial nerve
Actions - plantarflexes the foot at the ankle joint and because it crosses at the knee, it flexes there also.
Flexor hallucis longus
Found of the lateral side of the leg.
Origin - posterior surface of fibula.
Insertion - plantar surface of the phalanx of the great toe.
Innervation - tibial nerve
Action - flexes the great toe.
