Posterior Compartment of the Leg

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Components

Posterior leg compartment muscles	Origin	Insertion	Action	Nerve roots	Nerves
Accessory Soleus	Variable: often from anterior distal tibia or fibula, or from soleal line (distinct from main soleus)	Calcaneus (medial side) or medial Achilles tendon	Assists in ankle plantarflexion	S1 S2	Tibial nerve (branch of same segmental origin as soleus)
Flexor Digitorum Longus	Posterior surface of the tibia below the soleal line; fascia of tibialis posterior	Base of the distal phalanges of toes 2–5 (plantar surface)	Flexes lateral four toes (DIP, PIP, MTP), assists ankle plantarflexion and inversion, supports longitudinal arch	L5 S1 S2	Tibial nerve
Flexor Hallucis Longus	Inferior two-thirds of the posterior fibula and interosseous membrane	Base of the distal phalanx of the great toe (plantar surface)	Flexes the great toe (MTP and IP joints), assists plantarflexion, supports longitudinal arch	L5 S1 S2	Tibial nerve
Gastrocnemius	Lateral head – lateral condyle of femur (posterior aspect); Medial head – medial condyle of femur (popliteal surface above medial condyle)	Posterior calcaneus via calcaneal (Achilles) tendon	Plantarflexes ankle (especially with knee extended); flexes knee		Tibial nerve (S1–S2)
Plantaris	Lateral supracondylar ridge of the femur and oblique popliteal ligament	Calcaneus (medial to Achilles tendon) or into the Achilles tendon	Weak plantarflexion of ankle and knee flexion	L5 S1 S2	Tibial nerve
Popliteus	Lateral condyle of femur and lateral meniscus	Posterior surface of tibia above soleal line	Unlocks the knee by medially rotating tibia (or laterally rotating femur), weak knee flexion, stabilizes knee	L4 L5 S1	Tibial nerve
Soleus	Posterior aspect of head of fibula; proximal fibular shaft; soleal line of tibia; middle third of medial tibial border	Posterior calcaneus via calcaneal tendon	Plantarflexes ankle (independent of knee position); stabilizes leg over foot (postural)		Tibial nerve (S1–S2)
Tibialis Posterior	Posterior tibia (below soleal line), posterior fibula, and interosseous membrane	Navicular tuberosity, cuneiforms, cuboid, bases of 2nd–4th metatarsals	Inverts foot, assists plantarflexion, supports medial arch	L4 L5 S1	Tibial nerve

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