Pars profunda compartimenti posterioris cruris

• FLEXOR HALLUCIS LONGUS MUSCLE

• Origin: Inferior two-thirds of posterior surface of fibula; inferior part of interosseous membrane
• Insertion: Base of distal phalanx of big toe (hallux)
• Innervation: Tibial nerve (S1, S2)
• Main action: Flexes big toe at all joints; weakly plantarflexes ankle; supports medial longitudinal arch of foot

• TIBIALIS POSTERIOR MUSCLE

• Origin: Interosseous membrane; posterior surface of tibia inferior to soleal line; posterior surface of fibula
• Insertion: Tuberosity of navicular, cuneiform, cuboid, and sustentaculum tali of calcaneus; bases of 2nd, 3rd, and 4th metatarsals
• Innervation: Tibial nerve (L4, L5)
• Main action: Plantarflexes ankle; inverts foot

• FLEXOR DIGITORUM LONGUS MUSCLE:

• Origin: Medial part of posterior surface of tibia; by a broad tendon to fibula
• Insertion: Bases of distal phalanges of lateral four digits
• Innervation: Tibial nerve (S1, S2)
• Main action: Flexes lateral four digits; plantarflexes ankle; supports longitudinal arches of foot

• POPLITEUS MUSCLE:

• Origin: Lateral surface of lateral condyle of femur and lateral meniscus
• Insertion: Posterior surface of tibia, superior to soleal line
• Innervation: Tibial nerve (L4, L5, S1)
• Action: Weakly flexes knee and unlocks it by rotating femur 5 deg on fixed tibia; medially rotates tibia of unplanted limb

Blood supply:

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Posterior tibial artery.

Innervation:

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The posterior compartment of the leg is supplied by the tibial nerve.

Function:

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It contains the plantar flexors.