Tibialis Posterior

The tibialis posterior is a deep muscle of the posterior compartment of the leg. It arises from the posterior surfaces of the tibia and fibula and the intervening interosseous membrane, descends into a strong tendon, passes posterior to the medial malleolus, and inserts primarily onto the navicular with additional attachments to several bones of the midfoot.^[1][2]

Tibialis posterior is a powerful inverter of the foot and assists plantarflexion of the ankle. It is also one of the most important dynamic muscular supports of the medial longitudinal arch. Its tendon passes beneath the medial side of the foot and helps stabilize the hindfoot and midfoot during standing and walking.

The muscle is innervated by the tibial nerve and receives its principal arterial supply from branches of the posterior tibial and fibular arteries. Dysfunction of its tendon can lead to progressive collapse of the medial longitudinal arch and acquired flatfoot deformity.

Location

Tibialis posterior occupies a central position within the deep posterior compartment of the leg. It lies deep to soleus and between flexor digitorum longus medially and flexor hallucis longus laterally.

The muscle is closely related to the posterior surfaces of the tibia, fibula, and interosseous membrane.

Distally, the muscle narrows into a tendon that passes behind the medial malleolus before continuing toward the medial and plantar aspects of the foot.

General Anatomy

Feature	Anatomy
Muscle	Tibialis posterior
Compartment	Deep posterior compartment of leg
Origin	Posterior tibia, posterior fibula and interosseous membrane
Primary insertion	Navicular tuberosity
Additional insertions	Cuneiforms, cuboid and bases of selected metatarsals through tendinous expansions
Innervation	Tibial nerve
Root values	L4, L5
Blood supply	Posterior tibial and fibular arteries
Principal action	Inversion of foot
Secondary action	Plantarflexion of ankle
Arch function	Dynamic support of medial longitudinal arch

Origin

Tibialis posterior has an extensive origin from the posterior surface of the tibia, the posterior surface of the fibula, and the interosseous membrane between the two bones.^[1][3]

Its tibial origin lies inferior to the soleal line, while the fibular attachment occupies the medial aspect of the posterior fibula.

Additional fibers may arise from adjacent intermuscular septa and deep fascia.

Insertion

The principal insertion of tibialis posterior is onto the tuberosity of the navicular.

From this strong primary attachment, tendinous expansions extend to several neighboring bones. These commonly include the cuneiform bones, cuboid, and bases of the second through fourth metatarsals, although the exact pattern can vary.

The broad distal attachment allows tibialis posterior to influence multiple joints of the midfoot and contributes to its important role in maintaining the architecture of the foot.

Course

The muscle fibers descend through the deep posterior compartment and converge into a tendon in the distal leg.

The tendon passes posterior to the medial malleolus, where it changes direction toward the medial side of the foot.

It then courses anteriorly and inferiorly toward the navicular tuberosity before distributing additional slips across the plantar midfoot.

Deep Posterior Compartment

The deep posterior compartment contains four principal muscles:

• Popliteus
• Tibialis posterior
• Flexor digitorum longus
• Flexor hallucis longus

These muscles lie deep to the transverse intermuscular septum and the superficial posterior compartment.

They are supplied by the tibial nerve and receive blood from branches of the posterior tibial and fibular arteries.

Relations in the Leg

Tibialis posterior occupies a relatively central position in the deep posterior compartment. Flexor digitorum longus lies more medially, while flexor hallucis longus lies more laterally.

The posterior tibial neurovascular structures descend within the same deep compartment.

Soleus and the superficial posterior compartment lie superficial to tibialis posterior.

Relationship to the Interosseous Membrane

The interosseous membrane provides a substantial portion of the proximal attachment of tibialis posterior.

The membrane spans the interval between the tibia and fibula and separates the deep posterior structures from parts of the anterior compartment.

Its broad surface provides a stable origin from which tibialis posterior can generate force across the ankle and foot.

Relationship to Flexor Digitorum Longus

Flexor digitorum longus lies medial to tibialis posterior in the proximal and middle leg.

As the tendons approach the medial ankle, their arrangement becomes particularly important. The tibialis posterior tendon lies anterior to the flexor digitorum longus tendon behind the medial malleolus.

Both tendons pass through the tarsal tunnel region but continue toward different destinations in the foot.

Relationship to Flexor Hallucis Longus

Flexor hallucis longus lies lateral to tibialis posterior in the deep posterior compartment.

Its tendon passes behind the ankle and continues toward the great toe, whereas tibialis posterior turns toward the navicular and midfoot.

The tibial nerve and posterior tibial vessels occupy the interval between the flexor digitorum longus and flexor hallucis longus tendons in the retromalleolar region.

Relationship to the Medial Malleolus

The tibialis posterior tendon passes immediately posterior to the medial malleolus. The malleolus acts as a pulley, changing the direction of pull of the tendon from a predominantly vertical course in the leg to an anterior and plantar course in the foot.

The tendon lies within a fibro-osseous tunnel and is maintained against the underlying bone by the flexor retinaculum.

This sharp change in direction places substantial mechanical demands on the tendon during weight-bearing and gait.

Tarsal Tunnel

The tibialis posterior tendon is one of the structures passing deep to the flexor retinaculum on the medial side of the ankle.

From anterior to posterior, the major structures in this region are:

• Tibialis posterior tendon
• Flexor digitorum longus tendon
• Posterior tibial artery and accompanying veins
• Tibial nerve
• Flexor hallucis longus tendon

Tibialis posterior is therefore the most anterior of the major tendons passing behind the medial malleolus.

Flexor Retinaculum

The flexor retinaculum extends between the medial malleolus and the medial aspect of the calcaneus.

It forms the roof of the tarsal tunnel and retains the deep flexor tendons, vessels, and tibial nerve against the underlying bones.

The retinaculum prevents bowstringing of the tibialis posterior tendon as it changes direction around the medial malleolus.

Relationship to the Navicular

The navicular tuberosity is the principal distal attachment of tibialis posterior and is an important palpable landmark on the medial side of the foot.

The strong tendon inserts onto this prominence before distributing additional slips into the midfoot.

The position of the navicular within the medial longitudinal arch gives the tibialis posterior tendon considerable influence over arch height and midfoot stability.

Relationship to the Cuneiforms

Tendinous expansions of tibialis posterior commonly attach to the cuneiform bones.

These attachments distribute muscular force across the medial and central portions of the midfoot.

The broad insertion pattern allows tibialis posterior to stabilize several articulations simultaneously rather than acting through a single isolated attachment.

Relationship to the Metatarsals

Distal expansions of tibialis posterior may attach to the bases of the second, third, and fourth metatarsals.

These attachments contribute to the broad plantar distribution of the tendon and reinforce its influence across the midfoot.

The exact pattern and strength of these slips vary between individuals.

Innervation

Tibialis posterior is innervated by the tibial nerve, with root contributions primarily from L4 and L5.

The tibial nerve descends from the popliteal fossa into the posterior compartment and supplies the superficial and deep posterior muscles.

It continues behind the medial malleolus through the tarsal tunnel before dividing into its terminal plantar branches.

Blood Supply

Tibialis posterior receives blood from branches of the posterior tibial artery and fibular artery.

These vessels supply the deep structures of the posterior leg through muscular and perforating branches.

The vascular supply of the tibialis posterior tendon varies along its course, a consideration that is relevant to tendon degeneration and healing.

Actions

Inversion

Tibialis posterior is one of the major invertors of the foot. Its tendon passes posterior to the medial malleolus and inserts predominantly on the medial and plantar aspects of the midfoot.

Contraction elevates the medial side of the foot and turns the plantar surface toward the midline.

Tibialis posterior works with tibialis anterior during inversion.

Plantarflexion

Because its tendon passes posterior to the transverse axis of the ankle, tibialis posterior assists plantarflexion.

Its plantarflexion force is smaller than that produced by gastrocnemius and soleus, but it contributes to coordinated movement during gait.

Arch Support

Tibialis posterior is one of the most important dynamic supports of the medial longitudinal arch.

Its contraction draws the navicular and associated midfoot structures into a position that helps maintain the curvature and rigidity of the arch.

This muscular support complements the static support provided by the plantar ligaments, plantar aponeurosis, joint capsules, and bony architecture.

Medial Longitudinal Arch

The medial longitudinal arch extends from the calcaneus posteriorly through the talus, navicular, cuneiforms, and medial metatarsals.

Tibialis posterior supports this arch through its strong attachment to the navicular and broad tendinous expansions across the midfoot.

Loss of effective tibialis posterior function can permit progressive flattening of the arch and abnormal positioning of the hindfoot and forefoot.

Role During Gait

Tibialis posterior plays an important role during the stance phase of gait. After initial contact, the foot must accommodate the ground and subsequently become more rigid for propulsion.

Tibialis posterior helps control pronatory movements during weight acceptance and contributes to inversion and stabilization as the limb progresses through stance.

Later in stance, its activity helps create a more stable foot for transfer of force toward the forefoot and push-off.

Role in Hindfoot Control

Tibialis posterior exerts an important influence on the position of the hindfoot.

Its inversion force helps oppose excessive eversion and contributes to control of calcaneal alignment during weight-bearing.

This function is closely integrated with stabilization of the medial longitudinal arch and midfoot.

Relationship to Tibialis Anterior

Tibialis posterior and tibialis anterior are both strong invertors of the foot, but they have opposite effects on the ankle.

Tibialis posterior assists plantarflexion, while tibialis anterior produces dorsiflexion.

When the two muscles contract together, their opposing ankle actions can partially balance while their inversion forces reinforce one another.

Feature	Tibialis Posterior	Tibialis Anterior
Compartment	Deep posterior	Anterior
Innervation	Tibial nerve	Deep fibular nerve
Ankle action	Plantarflexion	Dorsiflexion
Foot action	Inversion	Inversion
Arch role	Major dynamic support	Contributes to medial arch support

Relationship to Fibularis Longus

Tibialis posterior and fibularis longus have opposing effects on inversion and eversion but share roles in plantarflexion and stabilization of the foot.

Tibialis posterior pulls from the medial side and produces inversion, whereas fibularis longus approaches from the lateral side and produces eversion.

Coordinated contraction can stabilize the foot while minimizing excessive movement in either direction.

Comparison with Deep Posterior Compartment Muscles

Muscle	Major Distal Attachment	Principal Function
Tibialis posterior	Navicular and midfoot	Inversion and arch support
Flexor digitorum longus	Distal phalanges of toes 2 to 5	Flexion of lateral four toes
Flexor hallucis longus	Distal phalanx of great toe	Flexion of great toe
Popliteus	Posterior proximal tibia	Unlocks knee and controls rotation

Anatomical Variations

The insertion of tibialis posterior is complex and demonstrates considerable individual variation.

The navicular remains the principal attachment, but the number, size, and destination of secondary tendon slips can differ. Variable attachments may involve the cuneiforms, cuboid, sustentaculum tali, and metatarsal bases.

Recognition of this broad insertional anatomy is important during imaging and reconstructive procedures.

Clinical Significance

Posterior Tibial Tendon Dysfunction

Posterior tibial tendon dysfunction occurs when the tibialis posterior tendon becomes unable to provide normal mechanical support to the foot.

Tendon degeneration, elongation, partial tearing, or rupture can reduce inversion strength and impair dynamic support of the medial longitudinal arch.

Progressive dysfunction can alter the alignment of the hindfoot and midfoot and produce an increasingly flattened foot.

Progressive Collapsing Foot Deformity

Dysfunction of the tibialis posterior tendon is strongly associated with progressive collapsing foot deformity, historically often described as adult-acquired flatfoot deformity.

As tendon function deteriorates, the medial longitudinal arch may descend while the hindfoot moves toward valgus and the forefoot develops compensatory malalignment.

The disorder can progress from a flexible deformity to more rigid structural changes involving multiple joints and supporting ligaments.

Tibialis Posterior Tendinopathy

Tibialis posterior tendinopathy commonly produces pain along the medial ankle and foot, particularly along the course of the tendon behind the medial malleolus and toward the navicular.

Repetitive loading and abnormal foot mechanics can increase mechanical stress on the tendon.

Because the tendon is essential for dynamic arch support, persistent dysfunction can have consequences extending beyond localized tendon pain.

Tendon Rupture

Partial or complete rupture of the tibialis posterior tendon can produce marked weakness of inversion and loss of dynamic medial arch support.

The resulting biomechanical imbalance allows the evertor muscles to act relatively unopposed and can contribute to progressive hindfoot valgus and arch collapse.

Ultrasound and MRI can be used to assess tendon continuity and associated soft-tissue abnormalities.

Single-Leg Heel-Rise Test

The single-leg heel-rise test is commonly used during clinical assessment of tibialis posterior function.

During a normal heel rise, plantarflexion is accompanied by inversion of the hindfoot as the heel lifts from the ground.

Significant tibialis posterior dysfunction can make repeated single-leg heel rises difficult or impossible and may reduce the expected inversion of the heel.

Accessory Navicular

An accessory navicular can occur near the navicular tuberosity, close to the principal insertion of tibialis posterior.

Depending on its morphology, the tibialis posterior tendon may attach partly or substantially to the accessory ossicle.

This relationship can alter tendon mechanics and may be associated with medial foot symptoms in some individuals.

Tarsal Tunnel Relationships

The tibialis posterior tendon passes through the same retromalleolar region as the tibial nerve and posterior tibial vessels.

Although the tendon itself is not a neural structure involved in tarsal tunnel syndrome, understanding its position is important when identifying the contents of the tunnel and planning surgical approaches.

Deep Posterior Compartment Syndrome

Tibialis posterior lies within the relatively confined deep posterior compartment. Increased pressure within this compartment can compromise muscular perfusion and neural function.

Compartment syndrome involving this region can affect tibialis posterior together with the other deep flexor muscles and the tibial neurovascular structures.

Imaging

Ultrasound and MRI are commonly used to evaluate the tibialis posterior tendon.

Ultrasound permits dynamic assessment and can demonstrate tendon thickening, fluid, tearing, and abnormal movement. MRI provides detailed evaluation of the muscle, tendon, surrounding retinacula, ligaments, and associated abnormalities of the foot.

Radiographs can additionally demonstrate changes in foot alignment and associated bony abnormalities such as an accessory navicular.

Surgical Anatomy

Tibialis posterior is important in reconstructive surgery involving the medial ankle, arch, and hindfoot.

Procedures may involve repair or reconstruction of the tendon, correction of associated deformity, or tendon transfer depending on the underlying pathology and structural changes.

Knowledge of the tendon course behind the medial malleolus and its broad insertion around the navicular and midfoot is essential during surgical exposure.

Surface Anatomy

The tibialis posterior muscle belly is deep and cannot normally be distinguished on routine surface examination.

Its tendon can be localized posterior and inferior to the medial malleolus and followed toward the navicular tuberosity on the medial side of the foot.

The tendon becomes functionally prominent during resisted inversion and plantarflexion. The palpable navicular tuberosity provides an important surface landmark for its principal distal attachment and for understanding the relationship between tibialis posterior and the medial longitudinal arch.