MSK 10a: posterior leg Flashcards
Innervations of the posterior leg muscles
Tibial nerve
General movements and insertions of the muscles
Superficial:
- gastrocnemius, soleus and plantaris
- insert onto calcaneal tendon
- perform plantar flexion
Deep:
- tibialis posterior, popliteus, flexor hallucis longus and flexor digitorum longus
- insert inferior to the medial malleolus
- perform ankle inversion
Layers separated by a band of fascia
Gastrocnemis
Medial and lateral heads originating from medial and lateral femoral condyles respectively, which converge to a single muscle belly
Insert onto calcaneal tendon
Action: plantar flexion at ankle when knee extended, and flexion at knee; therefore contain mainly fast-twitch fibres for powerful movements such as jumping
Soleus
Deep to gastrocnemius; large and flat
From soleal line (superior tibia) and proximal quarter of fibula, inserts onto calcaneal tendon.
Performs plantarflexion at the ankle with the knee in any position
Plantaris
A long tendon and small muscle, tendon can be mistaken for a nerve, and muscle absent in 10% of people. From inferior aspect of the lateral supracondylar line to the medial calcaneal tendon.
Usually assists knee flexion and plantar flexion of ankle
Tibialis posterior
Deepest muscle in posterior leg; lies between flexor digitorum longs and flexor hallucis longus. From superior tibia and fibula and interosseous membrane, to the inferior surfaces of the navicular, cuneiform, cuboid and the bases of the 2nd-4th metatarsals.
Performs plantar flexion at the ankle and inversion
Popliteus
Superiorly positioned posterior to the knee at the base of the popliteal fossa. From posterior surface of tibia to the lateral condyle of the femur (fibres travel superolaterally).
Unlocks the knee by laterally rotating the femur on the tibia
Flexor hallucis longus
Lateral side. From inferior two thirds of fibula and interosseous membrane to the base of the distal phalanx of the hallux.
Flexes (points) great toe at all joints and maintains the medial arch
Flexor digitorum longus
Smaller than FHL and more medial. From the media-posterior tibia (inferior to soleal line) to the base of the distal phalanges of the lateral four digits.
Flexes the lateral four digits and maintains the longitudinal arches
Mnemonic to remember order of tendons and neuromuscular structures at ankle (medial to lateral)
Tom-TP Dick-FDL And-posterior tibial artery Very-Vein Nervous-tibial nerve Harry-FHL
Ruptured calcaneal (Achille’s) tendon
Usually a partial tear but can be complete.
Sustained during forceful plantar flexion: hear a ‘snap’, and is more likely if had calcaneal tendonitis
Symptoms: pain, swelling, limp
Test with Thompson’s/Simmond’s test
Foot permanently dorsiflexed, soleus and gastrocnemius can contract to form a lump in the calf area. Treatment is usually non-surgical
Tibial nerve
L4 to S3; branch of sciatic nerve
Originates at the apex of the popliteal fossa and gives rise to the sural nerve (cutaneous). Runs posterior to the tibia and transmits cutaneous sensation from the sole of the foot.
Posterior tibial artery
Continuation of the popliteal artery. Supplies the posterior compartment and plantar foot. Notably palpable near the medial malleolus
Venae comitantes
Paired deep veins which run parallel to arteries. Pulsation of the arteries assists venous return, so especially useful in legs where the gravitational resistance is greatest
Describe the course of the deep veins of the lower limb
Medial and lateral plantar veins converge to join the posterior tibial vein, which runs posterior to the medial malleolus with the artery, Posterior tibial, anterior tibial and fibular veins drain into the popliteal vein, which then drains into the femoral vein. The femoral and profonda femoris (drains perforations in the thigh) veins then drain into the external iliac artery
Skeletal muscle pump and venae comitantes help venous return
